Digital PSAT Reading and Writing Practice Question 250: Answer and Explanation

Question: 250

Halley's Comet falls into a category called Great Comets, which are those that become bright enough during their passage near Earth to be observed by the naked eye. Predicting whether a comet will be “Great” has proven a challenging task even for the most talented astronomers and astrophysicists. The comet must pass through a relatively small expanse of space near enough to the sun to reflect a large amount of light but remain close enough to Earth for the light to reach and penetrate our atmosphere. Moreover, it is thought that a Great Comet must possess a large and active nucleus, though the exact physics of comet nuclei— which consist of dust, ice, and perhaps particulate minerals—are still poorly understood. Even so, comets meeting these criteria have on occasion failed to achieve “greatness.”

According to the text, which characteristic of a comet is most essential to its being categorized as a "Great Comet"?

• A. Whether it has a significant proportion of dust and ice in its core
• B. Whether it has an orbital eccentricity greater than zero
• C. Whether humans can observe it without a telescope
• D. Whether it contributes to meteor activity visible by astronomers

Correct Answer: C

Explanation:

C. The text defines a Great Comet as one that is bright enough to be observed by people on Earth with the naked eye. While the other options may be attributes of a Great Comet, they are not necessary ones.