A
Vacuum tubes are not now preferable to semiconductors for use in digital circuits.
B
Once vacuum tubes and semiconductors have comparable maximum current capacity, vacuum tubes will be used in some digital circuits.
C
The only reason that vacuum tubes are not now used in digital circuits is that vacuum tubes’ maximum current capacity is too low.
D
Semiconductors will always be preferable to vacuum tubes for use in many applications other than digital circuits.
E
Resistance to heat is the only advantage that vacuum tubes have over semiconductors.
A
Victims of the Ebola virus experience many symptoms that do not appear in any of the accounts of the Athenian epidemic.
B
Not all of those who are victims of the Ebola virus are afflicted with hiccups.
C
The Ebola virus’s host animals did not live in Athens at the time of the Athenian epidemic.
D
The Ebola virus is much more contagious than the disease that caused the Athenian epidemic was reported to have been.
E
The epidemics known to have been caused by the Ebola virus are usually shorter-lived than was the Athenian epidemic.
A
Environmentalists have been successfully maintaining the wolf population on Vancouver Island for 20 years.
B
As many wolves on Vancouver Island are killed by hunters as are born each year.
C
The population of wolves on Vancouver Island should be maintained by either reducing the number killed by hunters each year or introducing new wolves into the population.
D
The recent studies indicating that the total number of wolves on Vancouver Island has remained roughly constant for 20 years were flawed.
E
The stability in the size of the Vancouver Island wolf population does not warrant the article’s criticism of the environmentalists’ claim.
Computer scientist: For several decades, the number of transistors on new computer microchips, and hence the microchips’ computing speed, has doubled about every 18 months. However, from the mid-1990s into the next decade, each such doubling in a microchip’s computing speed was accompanied by a doubling in the cost of producing that microchip.
Summary
For several decades, the number of transistors on computer microchips has doubled every 18 months.
For several decades, microchips’ computing speed has also doubled every 18 months.
From the mid-1990s into the next decade, the cost of producing a microchip doubled each time the microchip’s computing speed doubled.
Very Strongly Supported Conclusions
From the mid-1990s into the next decade, the cost of producing a microchip doubled every 18 months.
From the mid-1990s into the next decade, the cost of producing a microchip doubled each time the number of transistors on a microchip doubled.
A
The only effective way to double the computing speed of computer microchips is to increase the number of transistors per microchip.
Unsupported. Doubling the number of transistors on a microchip is one effective way to double the computing speed of that microchip, but it’s not necessarily the only effective way.
B
From the mid-1990s into the next decade, there was little if any increase in the retail cost of computers as a result of the increased number of transistors on microchips.
Unsupported. We don’t know anything about how the retail cost of computers was affected by the increased number of transistors. We only know that, during this time period, the production cost of microchips doubled each time the number of transistors doubled.
C
For the last several decades, computer engineers have focused on increasing the computing speed of computer microchips without making any attempt to control the cost of producing them.
Unsupported. Just because microchip production costs increased from the mid-1990s into the next decade doesn’t mean that engineers made no effort to control those costs.
D
From the mid-1990s into the next decade, a doubling in the cost of fabricating new computer microchips accompanied each doubling in the number of transistors on those microchips.
Very strongly supported. During this time, production costs doubled each time a microchip’s speed doubled, and speed doubled each time the number of transistors doubled, so we know that production costs doubled each time the number of transistors doubled.
E
It is unlikely that engineers will ever be able to increase the computing speed of microchips without also increasing the cost of producing them.
Unsupported. Just because production costs doubled with microchip speed in the 90s doesn’t mean engineers can’t increase computing speed without raising costs in the future.
Aerobics instructor: Compared to many forms of exercise, kickboxing aerobics is highly risky. Overextending when kicking often leads to hip, knee, or lower-back injuries. Such overextension is very likely to occur when beginners try to match the high kicks of more skilled practitioners.
Summary
Compared to some other forms of exercise, kickboxing aerobics is highly risky. Overextending while kicking can cause hip, knee, or lower-back injuries. Overextension usually happens when beginners try to match the high kicks of skilled kickboxers.
Strongly Supported Conclusions
To reduce a person’s risk of injuries caused by overextension, that person should avoid overextending while kicking.
A
Skilled practitioners of kickboxing aerobics are unlikely to experience injuries from overextending while kicking.
This answer is unsupported. The aerobics instructor does not give us any information about the likelihood of skilled practitioners experiencing injuries.
B
To reduce the risk of injuries, beginners at kickboxing aerobics should avoid trying to match the high kicks of more skilled practitioners.
This answer is strongly supported. Since we know overextension can cause injury, then students should avoid overextending to reduce their risk of injury. An absent or reduced cause can lead to an absent or reduced effect.
C
Beginners at kickboxing aerobics will not experience injuries if they avoid trying to match the high kicks of more skilled practitioners.
This answer is unsupported. We don’t know if overextending while kicking is the only cause of injury to beginners. It is possible that beginners could experience injury some other way.
D
Kickboxing aerobics is more risky than forms of aerobic exercise that do not involve high kicks.
This answer is unsupported. We know that kickboxing aerobics is more risky than many forms of exercise, but we don’t know whether this comparison is to other forms that do not involve high kicks.
E
Most beginners at kickboxing aerobics experience injuries from trying to match the high kicks of more skilled practitioners.
This answer is unsupported. We do not know whether most beginners will for a fact overextend while kicking.