Beginning in the mid-nineteenth century, discussion about the possibil

OFFICIAL EXPLANATION

Overview:

Questions reference a passage that discusses the early research about the possibility of life on Mars. The passage begins by explaining that scientists have been considering this topic “in earnest” since the middle of the nineteenth century. The English scientist William Whewell claimed that Mars might have a similar landscape to Earth. Additionally, scientists discovered that Mars has days just over 24-hours long, although the seasons are twice as long as seasons on Earth given the axial tilt in combination with the elongation of the orbit of Mars. Late nineteenth-century scientists observed that there appeared to be canals on the planet, and there was argument about previous civilizations. But the later work of scientists with more powerful telescopes discovered that Mars has no water or oxygen in its atmosphere.

Question asks the student to select the answer choice that is strictly implied within the statements about canals on Mars, so the student needs to review each answer choice carefully and compare each one to the statements in the passage. The correct answer choice will be an inference, but this inference will only utilize the information provided in the passage and will not assume more than the passage can explain.

The Correct Answer:

E Answer choice (E) offers a clear link between the fourth and fifth sentences of the passage. The author of the passage notes that some scientists claimed to see canals on the surface of Mars and argued for the presence of intelligent life, while later scientists discovered that there was no water or oxygen in the atmosphere of Mars. From this, the student may deduce that the discovery of the lacking elements in Mars’s atmosphere made it impossible for earlier civilizations to exist there. Therefore, the “canals” must have been confused with some other feature on the landscape of Mars, and answer choice (E) is correct. (Note: This is also historically true. Stronger telescopes revealed that what were assumed to be canals did not actually exist on the surface of Mars.)

The Incorrect Answers:

A The passage is not entirely clear about who was believed to have inhabited the “earlier civilizations” rumored to have lived on Mars, but the author does imply that the earlier civilizations would have required water and oxygen, and the belief about the life was related to “intelligent life forms.” From this, the student may infer that earlier civilizations with intelligent beings (similar to humans, if not actually humans) were likely believed to have been on Mars, and the author is proving this theory incorrect with the discovery of the lacking elements in Mars’s atmosphere. The student cannot infer from the information in this passage alone, however, that all life forms require water and oxygen. Answer choice (A) infers more than the passage is focused on implying, so it is incorrect.

B As indicated in answer choice (A), the author of the passage seems to be implying that the previous inhabitants on the surface of Mars were believed to be human or similar to human beings in their intelligent ability to develop civilizations (that included canals). Answer choice (B), therefore, is also incorrect.

C The author of the passage implies strongly that the canals—as they were observed—did not even exist and were confused with another feature on the landscape of Mars. The passage notes that William Wallace and others were able to “debunk the canal theory”; as such, it cannot be inferred that there were canals at all. Answer choice (C) cannot be correct.

D The passage indicates clearly that William Wallace was but one scientist whose research indicated the canal theory to be impossible, so he alone cannot be credited with debunking it. Answer choice (D) assumes too much, so it is also incorrect.