Astronomy current events question: Vesta northern vs. southern hemispheres

Astronomy 210L, fall 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!)

Astronomy.com editors, "Dawn at Vesta: Massive Mountains, Rough Surface, and Old-Young Dichotomy in Hemispheres," October 4, 2011
http://www.astronomy.com/News-Observing/News/2011/10/Dawn%20at%20Vesta%20-%20massive%20mountains%20-%20rough%20surface%20-%20and%20old-young%20dichotomy%20in%20hemispheres.aspx

__________ observed by the NASA Dawn spacecraft is evidence that the southern hemisphere of the asteroid Vesta may be much younger than its northern hemisphere.
(A) Different color features.
(B) The number of craters per area.
(C) Warm thermal vents.
(D) Rotation rate fluctuations.
(E) Subterranean oceans.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 7 students
(B) : 33 students
(C) : 2 students
(D) : 1 student
(E) : 3 students