Astronomy quiz question: cause of changing lunar phases

Astronomy 210 Quiz 1, spring semester 2015
Cuesta College, San Luis Obispo, CA

__________ causes the different phases of the moon.
(A) Earth's revolution around the sun.
(B) Earth's rotation about its own axis.
(C) The moon's revolution around Earth.
(D) The moon's rotation about its own axis.

Correct answer (highlight to unhide): (C)

The approximately 28-day "moonth" cycle of the moon's phases is caused by the moon's approximately 28-day revolution in its orbit around Earth. (The 24-hour rotation of Earth about its own axis causes the moon (which is essentially stationary with respect to Earth over the course of a day) to appear to rise and set over approximately 10-14 hours for an observer in San Luis Obispo, CA.)

Section 30674
Exam code: quiz01nW0r
(A) : 5 students
(B) : 3 students
(C) : 34 students
(D) : 2 students

Success level: 78% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.13