3. The “serious problem” referred to in line 17 could be solved if which of the following were true?

Difficulty Level: Very Hard

Explanation

Which one of the five options would, if true, indicate a possible solution to the serious problem referred to? The serious problem is said to arise from the relative lack of energy radiating from the galactic center compared with the expected value if a matter-engulfing black hole were truly at the center of the Milky Way.

According to the passage, the radiated energy turned out to be a few thousand times less than had been expected, on theoretical grounds, to radiate from mass engulfed by the hypothetical black hole. However, if it were discovered that the matter engulfed were several thousand times less than previously estimated, the relatively low level of radiated energy observed would no longer seem at odds with the existence of the hypothesized black hole.

A. Correct. Reviewing the assumptions underlying the widely held predictions could lead to revised predictions that harmonize with the observational evidence regarding radiated energy from the galaxy's center.

B. The passage states that the assumed quantity of engulfed matter already seems to be radiating too little; this answer choice would actually make the “serious problem” in the passage worse. That is, assuming that there is actually more engulfed matter with such a small amount of radiation would simply worsen the problem.

C. The passage does not specify what impact a greater-than-estimated density would have on the quantity of energy that is radiated. That is, even if greater mass would change predictions, greater density may not do so.

D. If the object were more massive, then presumably the matter engulfed by this hypothetical more massive black hole would radiate a quantity of energy even greater than the observed quantity. This again would simply make the “serious problem” worse.

E. Given that not enough radiated energy is currently being observed, finding that the matter being engulfed radiates even more energy than expected would make the “serious problem” significantly worse. That is, the relatively low quantity of radiated energy observed would fall even farther short of the quantity expected.

The correct answer is A.

4. The “widely held predictions” mentioned in line 25 are predictions about the

Difficulty Level: Medium

Explanation

What do the “widely held predictions” mentioned in the passage's final sentence refer to? Notice that the final sentence of the passage refers to a comparison between two things: the energy coming from the galactic center and the quantity of energy widely predicted to be radiated from matter being engulfed by a black hole. It follows that the best answer should present an option that refers to a predicted quantity of energy.

A. This choice fails to refer to any predicted quantity of energy.

B. This choice fails to refer to any predicted quantity of energy.

C. This choice fails to refer to any predicted quantity of energy.

D. This choice fails to refer to any predicted quantity of energy.

E. Correct. This choice presents the only option that refers to a predicted quantity of energy.

The correct answer is E.