Archaeologist: For 2,000 years the ancient Sumerians depended on irrigation to sustain the agriculture that fed their civilization. But eventually irrigation built up in the soil toxic levels of the salts and other impurities left behind when water evaporates. When its soil became unable to support agriculture, Sumerian civilization collapsed. A similar fate is thus likely to befall modern civilizations that continue to rely heavily on irrigation for agriculture.

Summarize Argument
The author concludes that modern civilizations that continue to rely heavily on irrigation for agriculture are likely to collapse. This is based on a comparison to the ancient Sumerian civilization, which relied on irrigation for agriculture. After irrigation built up toxic levels of salts and other impurities in the soil, the Sumerian civilization collapsed.

Notable Assumptions
The author assumes that the problem of toxic levels of salts and other impurities faced by the Sumerians is likely to face modern civilizations that rely on irrigation for agriculture.

A
Most modern civilizations could not feed themselves through agriculture without relying heavily on irrigation.
This suggests modern civilizations need irrigation to feed themselves through agriculture. But this doesn’t relate to whether such reliance will lead to collapse from toxic soil.
B
Factors unrelated to the use of irrigation would probably have caused Sumerian civilization to collapse sooner or later.
Even if other factors would have led to the Sumerian collapse, that doesn’t change the fact that toxic soils contributed to the Sumerian collapse or whether what happened to the Sumerians will happen to modern civilizations.
C
Many modern farmers use irrigation techniques that avoid the buildup of salts and other toxic impurities in the soil.
This points out why what happened to the Sumerians might not happen to modern civilziations. Modern techniques might not lead to toxic levels of salt and impurities in soil.
D
Many modern civilizations do not rely to any significant extent on irrigation for agriculture.
We’re concerned with what happens to the ones that do rely on irrigation for agriculture. But whether these kinds of civilization are common or rare doesn’t relate to whether these kinds, however many there are, will collapse.
E
The soil of ancient Sumeria already contained some toxic salts and other impurities before the Sumerians started using irrigation for agriculture.
We have no reason to think modern soil doesn’t also contain some toxic salts and other impurities. In addition, even if modern soil doesn’t already have this, that just means it might take longer for the collapse. But (E) doesn’t suggest there wouldn’t be a collapse.

23 comments

Researcher: Dinosaur fossils come in various forms, including mineralized bones and tracks in dried mud flats. However, mineralized dinosaur bones and dinosaur tracks in dried mud flats are rarely found together. This isn’t surprising, because creatures that scavenged dinosaur carcasses most likely frequented mud flats to find food.

Summarize Argument: Phenomenon-Hypothesis

The researcher concludes that it isn’t surprising that dinosaur bone fossils are rarely found near fossilized dinosaur tracks in mud flats. This observation is explained with the hypothesis that animals that scavenged dinosaur carcasses often searched for food in mud flats.

Notable Assumptions

The researcher assumes that dinosaur bones could have been moved away from the dinosaur tracks by the activity of creatures that scavenge dinosaur bones in mud flats. The researcher also assumes that there isn’t an alternate explanation for dinosaur bones and tracks often being separated in mud flats.

A
Dinosaur tracks are also found in locations other than mud flats.

This is irrelevant, since the the researcher’s hypothesis only aims at explaining dinosaur tracks that are in mud flats; no conclusions are being drawn about other types of locations.

B
Scavengers commonly drag a carcass away from the site where it was found.

This strengthens the argument by providing a mechanism for the separation of dinosaur bones from tracks by scavenger activity. This affirms the researcher’s assumption that scavenger activity can lead to tracks and bones being separated.

C
Researchers have found more fossil dinosaur tracks than fossil dinosaur bones.

This is irrelevant, since the hypothesis doesn’t depend on the relative frequency of tracks and bones, only the observation that they are rarely found together in mud flats.

D
Dinosaur fossils other than mineralized bone or tracks in dried mud flats are quite common.

This is irrelevant, since the researcher doesn’t make any claims about other types of dinosaur fossils, and only seeks to explain why bones and tracks are rarely found together in mud flats.

E
It takes longer for bone to mineralize than it takes for tracks to dry in mud flats.

This is irrelevant, because how long bones take to mineralize has no bearing on whether or how those bones can be moved away from their original location by scavengers.


12 comments

Electric stovetop burners would cause fewer fires if their highest temperature were limited to 350ºC (662ºF), which provides more than enough heat for efficient and effective cooking. The lowest temperature at which cooking oil and most common fibers ignite is 387ºC, and electric burners on high go well above 700ºC.

Summarize Argument: Causal Explanation
The author tells us that limiting the temperature of electric stove burners to 350°C would cause fewer fires. This is supported in two ways: first, by telling us that some flammable items (oil and most fabric) need to be heated above this point to catch fire; and second, by stating that electric burners can currently go far above the temperature needed to ignite these items. By establishing that a fire risk currently exists, and that this limit would reduce or eliminate it, the author supports the conclusion that setting the limit would lead to fewer fires.

Identify Conclusion
The conclusion is the author’s claim about lowering fire risk: “Electric stovetop burners would cause fewer fires if their highest temperature were limited to 350°C (662°F).”

A
Electric stovetop burners would cause fewer fires if their highest temperature were limited to 350ºC.
This is where the author states the conclusion. Everything else in the argument is meant to convince us that this claim is true.
B
A maximum temperature of 350ºC provides more than enough heat for efficient and effective cooking.
This is used to explain that stoves would still be useful with the proposed limitation, but doesn’t actually form part of the argument about lowering fire risk. This is not supported by anything else, nor does it provide support to the conclusion.
C
The lowest ignition temperature for cooking oil and most common fibers is 387ºC.
This is a premise that supports the conclusion, because it shows that keeping stoves below this temperature would mean a lower risk that oil and fabric near the stove could catch fire.
D
Electric burners on high go well above 700ºC.
This is a premise that supports the conclusion, because it shows that stoves currently reach a high enough temperature to ignite some materials that might come near the burners.
E
Electric stovetop burners cause fires because they go well above 700ºC when set on high.
The argument implies that this is true, but this claim acts as support for the conclusion that limiting stovetop temperatures would reduce the number of fires. That makes it a sub-conclusion at best, not the main conclusion.

3 comments

Supervisor: Our next budget proposal will probably be approved, because normally about half of all budget proposals that the vice president considers are approved, and our last five budget proposals have all been turned down.

A
the last five budget proposals’ having been turned down guarantees that the next five budget proposals will be approved
The supervisor doesn’t discuss the likelihood of the next five budget proposals being approved. The supervisor only argues that the next budget proposal will probably be approved.
B
the vice president is required to approve at least half of all budget proposals submitted
The supervisor never states or implies that the vice president must approve at least half of all budget proposals. The supervisor only says that roughly half of all budget proposals considered by the vice president end up being approved.
C
having the last five budget proposals turned down affects the likelihood that the next budget proposal will be turned down
This is an unexplained assumption made by the supervisor. The supervisor provides no reason to believe that the last five budget proposals being rejected has any bearing on the likelihood of the next budget proposal being approved.
D
the majority of the last five budget proposals deserved to be turned down
The supervisor’s argument isn’t concerned with whether the last five budget proposals should’ve been turned down.
E
the likelihood that a budget proposal will be approved is influenced by the amount of money that budget proposal requests
The supervisor never discusses the amount of money requested by any budget proposals.

8 comments