Astronomy current events question: Titan's methane and ethane rivers and lakes

Astronomy 210L, spring 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!)

Camille Carlisle, "Big River on Titan," December 12, 2012
http://www.skyandtelescope.com/news/River-on-Titan-183195881.html

Liquid methane and ethane rivers and lakes on Saturn's moon, Titan, appear black in NASA Cassini spacecraft radar images because methane and ethane:
(A) reflect or absorb radar signals.
(B) have similar properties to crude oil.
(C) only emit infrared light.
(D) are constantly flowing.
(E) are much colder than Titan's crust.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 43 students
(B) : 4 students
(C) : 7 students
(D) : 2 students
(E) : 2 students