Microbiology: Commensal Bacteria

Bacteria that benefit human beings when they are present in the body are called commensals. The bacterium Helicobacter pylori plays a primary role in the development of stomach ulcers. But since stomach ulcers occur in less than 10 percent of those harboring H. pylori, and since it allegedly strengthens immune response, many scientists now consider it a commensal. But this is surely misguided. Only about 10 percent of the people who harbor Mycobacter tuberculosis—a bacterium that can cause tuberculosis—get sick from it, yet no one would call M. tuberculosis a commensal.

Which one of the following, if true, most seriously undermines the argument's reasoning?

Mayor: There has been a long debate in city council about how to accommodate projected increases in automobile traffic. Today, our choice is clear: either we adopt my plan to build a new expressway, or we do nothing. Doing nothing is not a viable option because our existing system of roads would be in gridlock within ten years given even a conservative estimate of future traffic levels. City council should therefore adopt my plan.

The reasoning in the mayor's argument is most vulnerable to which one of the following criticisms?

Museum curator: Our ancient Egyptian collection includes an earthenware hippopotamus that resembles a child's toy. It was discovered in a tomb, upside down, with its legs broken off. We know that the ancient Egyptians believed the dead had to wage eternal war with beasts. Breaking the legs off a representation of an animal was thought to help a deceased person in this war. We conclude that, far from being a toy, this hippopotamus was a religious object.

Which one of the following is an assumption required by the curator's argument?

Lawyer: Juries are traditionally given their instructions in convoluted, legalistic language. The verbiage is intended to make the instructions more precise, but greater precision is of little use if most jurors have difficulty understanding the instructions. Since it is more important for jurors to have a basic but adequate understanding of their role than it is for the details of that role to be precisely specified, jury instructions should be formulated in simple, easily comprehensible language.

Each of the following, if true, strengthens the lawyer's argument EXCEPT:

Traditional “talk” therapy, in which a patient with a psychological disorder discusses it with a trained therapist, produces chemical changes in the brain. These changes seem to correspond to improvements in certain aspects of the patient's behavior. Thus, physicians will eventually be able to treat such patients as effectively through pharmacological intervention in the brain's neurochemistry as through the lengthy intermediary of traditional “talk” methods.

Which one of the following is an assumption on which the argument depends?

Most apartments on the upper floors of The Vista Arms apartment building have scenic views. So there is in the building at least one studio apartment with scenic views.

The conclusion of the argument follows logically if which one of the following is assumed?

Mike: Tom did not tell me that I could use his computer, but it would not be wrong for me to use it anyway. Last week Tom used Mary's bicycle even though she had not told him he could use it.

Which one of the following principles, if valid, would most help to justify Mike's reasoning?

Robinson: Wexell says that the museum wasted its money in purchasing props and costumes from famous stage productions, because such items have no artistic significance outside the context of a performance. But many of the props and costumes are too old and fragile for use in a performance. So clearly, the museum did not waste its money, for displaying these items is the only way of making them available to the public.

The reasoning in Robinson's argument is most vulnerable to criticism on the grounds that it

In a party game, one person leaves the room with the understanding that someone else will relate a recent dream to the remaining group. The person then returns and tries to reconstruct the dream by asking only yes-or-no questions. In fact, no dream has been related: the group simply answers the questions according to some arbitrary rule. Surprisingly, the person usually constructs a dream narrative that is both coherent and ingenious.

The example presented above most closely conforms to which one of the following propositions?

Computer manufacturers have sought to make computer chips ever smaller, since decreasing the size of a computer's central processing unit (CPU) chip—without making that CPU chip any less sophisticated—will proportionally increase the speed of the CPU chip and the computer containing it. But since CPU chips cannot be made significantly smaller without decreasing their sophistication, computers cannot currently be made significantly faster.

Which one of the following is an assumption on which the argument depends?