Astronomy current events question: fragile asteroids?

Astronomy 210L, fall semester 2013
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)

Mark Zastrow, "Under Stress, Asteroids May Be Fragile," August 7, 2013
http://www.skyandtelescope.com/news/Under-Stress-Asteroids-May-Be-Fragile-218731091.html

A European research team has proposed that surfaces of asteroids may be extremely unstable, based on:
(A) the moon's polar ice caps.
(B) rubble piles on Mars.
(C) Mojave desert sand dunes.
(D) experiments on airplanes.
(E) melting glaciers in Antarctica.

Correct answer: (D)

Student responses
Sections 70178, 70186, 70200
(A) : 19 students
(B) : 24 students
(C) : 3 students
(D) : 18 student
(E) : 2 students