Astronomy quiz question: time for Pisces to set

Astronomy 210 Quiz 1, spring semester 2017
Cuesta College, San Luis Obispo, CA

The diagram at right shows the positions on March 21 of the sun and the zodiac constellations Aries and Pisces for an observer in San Luis Obispo, CA. Ignore daylight saving time. Assume you can see stars in daylight. On this day, the last part of the constellation Pisces will completely set below the horizon __________ later.
(A) three hours.
(B) six hours.
(C) nine hours.
(D) 12 hours.

Correct answer (highlight to unhide): (C)

As read off from a starwheel, Pisces is above the south horizon as shown at 12:00 PM on March 21. (Also since the sun is also centered on the south horizon, on the meridian, this must be 12:00 PM). Advancing time forward (while keeping the date at March 21) indicates that Pisces will completely set nine hours later that same day.

Section 30674
Exam code: quiz01nK0n
(A) : 0 students
(B) : 5 students
(C) : 17 students
(D) : 1 student

Success level: 76% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.17

Section 30676
Exam code: quiz01s7vN
(A) : 2 students
(B) : 10 students
(C) : 34 students
(D) : 1 student

Success level: 73% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.54