Cora: To ask this question, you must be making a mistaken assumption: that typing speed was to be maximized. The real danger with early typewriters was that operators would hit successive keys too quickly, thereby crashing typebars into each other, bending connecting wires, and so on. So the idea was to slow the operator down by making the most common letter sequences awkward to type.
Bernard: This is surely not right! These technological limitations have long since vanished, yet the keyboard is still as it was then.
Summarize Argument
Bernard concludes that the standard typewriter keyboard could not have been designed to slow the typer down. This is because the technological limitations that could lead to problems from fast typing are no longer around, but the keyboard design is still the same.
Notable Assumptions
Bernard assumes that the standard keyboard would be changed to allow for faster typing once the technological limitations around when the keyboard was originally designed are no longer present. (Maybe there are strong reasons that the keyboard wouldn’t be changed, even if we don’t need to slow people down anymore.)
A
Typewriters and word-processing equipment are typically sold to people who have learned to use the standard keyboard and who, therefore, demand it in equipment they buy.
This is a reason the keyboard design wouldn’t change, even when the technological limits are no longer present. People grew up with the slower-typing design and still want it today. This is why the fact people still use the design today doesn’t undermine Cora’s explanation.
B
Typewriters have been superseded in most offices by word-processing equipment, which has inherited the standard keyboard from typewriters.
Bernard believes the fact people still use the same design shows that the design couldn’t have been intended to slow people down. (B) simply affirms that the same design is used today, which we already knew. But it doesn’t suggest why the same design is used today, unlike (A).
C
The standard keyboard allows skilled operators to achieve considerable typing speeds, though it makes acquiring such skills relatively difficult.
Pointing out that the design still allows fast typing doesn’t engage with Bernard’s reasoning. We want to show how the design could have been intended to slow people down, despite the fact we still use the design today.
D
A person who has learned one keyboard layout can readily learn to use a second one in place of the first, but only with difficulty learn to use a second one alongside the first.
This supports Bernard’s reasoning. After all, why aren’t people changing to a faster layout if we don’t need to slow people down anymore? Bernard’s suggestion is that the lack of change implies slowing people down couldn’t be the original purpose of the design.
E
It is now possible to construct typewriters and word-processing equipment in which a single keyboard can accommodate two or even more different keyboard layouts, each accessible to the operator at will.
This supports Bernard’s reasoning. If the keyboard can be changed to accommodate a different layout, then why hasn’t the keyboard changed if it was originally intended to slow people down? To Bernard, the lack of change implies the original purpose wasn’t to slow down typing.
Summary
Fishery officials are still considering options to eliminate a breed of pike from Lake Davis. Introducing disease and draining the lake have been ruled-out as options. Four years ago, poison was added to the lake and caused an outrage among residents.
Strongly Supported Conclusions
The poison added to Lake Davis four years earlier must not have been successful in eliminating the pike.
A
Draining the lake would not cause the region’s tourism economy to suffer.
We know that draining the lake is not an option for eliminating the pike from Lake Davis, but we do not know why this option was ruled out by Fishery officials.
B
Four years ago was the only time that poison was used against the pike in the lake.
We don’t know whether or not poison was introduced into Lake Davis only once in attempt to eliminate the pike.
C
The poison added to the lake four years ago was not successful in ridding the lake of the pike.
The poison added to Lake Davis must not have been successful in eliminating the pike, since Fishery officials are still considering options for the pike’s elimination.
D
Four years ago, fishery officials did not consider any options other than using poison.
We don’t know what options Fishery officials were considering four years ago in order to eliminate the pike from Lake Davis. We know that they eventually decided to use poison, but there could have been other options they were considering.
E
Salmon and trout populations in the Lake Davis area are essential to the region’s economy.
We know that the pike in Lake Davis threatens the lake’s population of salmon and trout, but we do not know if these two fish species are essential for the economy.
Summary
People with cat allergies are allergic to certain proteins in a cat’s skin secretions and saliva. It depends on the allergy sufferer which proteins are responsible for an allergic reaction. There is no such thing as a cat incapable of provoking allergic reactions, because all cats shed skin and spread saliva around the environment. However, it is common for a single cat to cause an allergic reaction in some people and not all people allergic to cats.
Strongly Supported Conclusions
Different cats have different proteins in their skin secretions and saliva.
A
Any particular individual will be allergic to some breeds of cat but not to others.
This answer is unsupported. The stimulus is limited to people with cat allergies. We cannot say that all individuals have cat allergies based on the stimulus.
B
No cat is capable of causing an allergic reaction in all types of allergy sufferers.
This answer is unsupported. We only know from the stimulus that it is common for a single cat to cause allergic reactions in some people but not others. There could be a cat in existence that can cause a reaction in all cat allergy sufferers.
C
Not all cats are identical with respect to the proteins contained in their skin secretions and saliva.
This answer is strongly supported. If it’s common for some cats to cause allergic reactions in some people but not all people, then cats must differ in their allergy-causing proteins.
D
The allergic reactions of some people who are allergic to cats are more intense than the allergic reactions of other allergy sufferers.
This answer is unsupported. We don’t know from the stimulus how intense an allergic reaction from a cat could be.
E
There is no way to predict whether a given cat will produce an allergic reaction in a particular allergy sufferer.
This answer is unsupported. If we know what proteins a particular person is allergic to and what proteins a particular cat secretes, it could be possible to predict an allergic reaction.
Summary
The argument concludes that passengers are safer on airplanes with a collision-evasion system equipped, even though the system frequently warns pilots of phantom airplanes. This is supported by the premise that the system warns pilots to evade possible collisions.
Notable Assumptions
The argument assumes that the phantom warnings don’t create more danger than the system prevents. For example, that pilots don’t take dangerous evasion maneuvers in response to phantom warnings.
It also assumes that pilots actually respond to the system’s warnings frequently enough to avoid possible collisions. Otherwise, the system’s presence wouldn’t make much difference to safety at all.
It also assumes that pilots actually respond to the system’s warnings frequently enough to avoid possible collisions. Otherwise, the system’s presence wouldn’t make much difference to safety at all.
A
Passengers feel no safer on airplanes equipped with the radar system than on comparable airplanes not so equipped.
Whether or not passengers feel safer isn’t important to determining whether or not they are safer—in fact, it’s not relevant at all.
B
Warnings given by a collision-avoidance system about phantom airplanes are not caused by distorted radar signals.
The possible cause of phantom airplane warnings doesn’t make any difference to the argument, so can’t be necessary.
C
The frequency of invalid warnings will not cause pilots routinely to disregard the system’s warnings.
For the argument to make sense, pilots have to actually act on the system’s warnings—otherwise the system would make no difference. If we negated this, meaning pilots just ignored the warnings, that would leave the conclusion unsupported.
D
Commercial passenger airplanes are not the only planes that can be equipped with a collision-avoidance system.
Whether or not the system can be equipped on other types of planes is irrelevant to whether it makes commercial air passengers safer.
E
The greatest safety risk for passengers traveling on commercial passenger airplanes is that of a midair collision.
The argument just claims that passengers are safer with the system than without it. Whether that means they’re a lot safer or a little safer doesn’t really matter, so this isn’t a necessary assumption.