Reading Comprehension
试题详情
文章：
| Line | When asteroids collide, some collisions cause |
| an asteroid to spin faster; others slow it down. If | |
| asteroids are all monoliths—single rocks—undergoing | |
| random collisions, a graph of their rotation rates | |
| (5) | should show a bell-shaped distribution with statistical |
| “tails” of very fast and very slow rotators. If asteroids | |
| are rubble piles, however, the tail representing the | |
| very fast rotators would be missing, because any | |
| loose aggregate spinning faster than once every few | |
| (10) | hours (depending on the asteroid’s bulk density) |
| would fly apart. Researchers have discovered that | |
| all but five observed asteroids obey a strict limit on | |
| rate of rotation. The exceptions are all smaller than | |
| 200 meters in diameter, with an abrupt cutoff for | |
| (15) | asteroids larger than that. |
| The evident conclusion—that asteroids larger than | |
| 200 meters across are multicomponent structures or | |
| rubble piles—agrees with recent computer modeling | |
| of collisions, which also finds a transition at that | |
| (20) | diameter. A collision can blast a large asteroid to bits, |
| but after the collision those bits will usually move | |
| slower than their mutual escape velocity. Over several | |
| hours, gravity will reassemble all but the fastest | |
| pieces into a rubble pile. Because collisions among | |
| (25) | asteroids are relatively frequent, most large bodies |
| have already suffered this fate. Conversely, most | |
| small asteroids should be monolithic, because impact | |
| fragments easily escape their feeble gravity. |
题目：
The author of the passage mentions “escape velocity” (see line 22) in order to help explain which of the following?
选项:
A、The tendency for asteroids to become smaller rather than larger over time
B、The speed with which impact fragments reassemble when they do not escape an asteroid’s gravitational attraction after a collision
C、The frequency with which collisions among asteroids occur
D、The rotation rates of asteroids smaller than 200 meters in diameter
E、The tendency for large asteroids to persist after collisions
答案:
E
