Astronomy current events question: Gliese 581g eyeball?

Astronomy 210L, Spring Semester 2011
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!)

Rachel Courtland, "Is First Life-Friendly Exoplanet an 'Eyeball'?," January 13, 2011
http://www.newscientist.com/article/mg20927953.700-is-first-lifefriendly-exoplanet-an-eyeball.html

According to a University of Chicago researcher, the recently discovered exoplanet Gleise 581g may resemble an eyeball because:
(A) of its extremely dense, collapsed core.
(B) ice on the side facing its star would melt.
(C) its optical properties would focus light.
(D) its lopsided core protrudes above its surface.
(E) of a large impact crater centered on its north pole.

Correct answer: (B)

Student responses
Sections 30678, 30679, 30680
(A) : 12 students
(B) : 35 students
(C) : 5 students
(D) : 2 students
(E) : 4 students