Astronomy current events question: end date of Mercury's volcanic activity

Astronomy 210L, fall semester 2016
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!)

Tracey Peake, "Most Volcanic Activity on Mercury Stopped About 3.5 Billion Years Ago" (August 5, 2016)
news.ncsu.edu/2016/08/byrne-mercury/

According to North Carolina State University researchers, volcanic activity on Mercury ended about 3.5 billion years ago, as found from dating volcanic deposits using __________ data.
(A) surface hardness.
(B) reflectivity.
(C) chemical analysis.
(D) radioactive decay.
(E) crater size and number.

Correct answer: (E)

Student responses
Sections 70178, 70186
(A) : 2 students
(B) : 5 students
(C) : 3 students
(D) : 8 students
(E) : 16 students