Astronomy quiz question: comparative surface dating of Mercury's surface

Astronomy 210 Quiz 4, spring semester 2015
Cuesta College, San Luis Obispo, CA

Compared to the oldest surfaces on Mercury, the more recently developed surfaces have __________ craters.
(A) fewer.
(B) volcanic.
(C) darker.
(D) collapsed.

Correct answer (highlight to unhide): (A)

Because of the rate of bombardment in the solar system has decreased over time, the density of impact craters indicates the surface age of a terrestrial planet, where a heavily cratered region is relatively older than a region with fewer craters, which would have experienced more recent geological activity that would remove/cover craters.

Section 36074
Exam code: quiz04NoR3
(A) : 26 students
(B) : 5 students
(C) : 4 students
(D) : 3 students

Success level: 71% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.60

Section 30676
Exam code: quiz04s0U7
(A) : 37 students
(B) : 1 student
(C) : 3 students
(D) : 5 students

Success level: 80% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.54