Astronomy quiz question: Mars and Jupiter as morning stars?

Astronomy 210 Quiz 2, fall semester 2013
Cuesta College, San Luis Obispo, CA

The locations of Earth, Mars and Jupiter are shown in the diagram below (not to scale, and orbits have been simplified as circles instead of ellipses).

Which planets will be "morning stars" (visible just before sunrise (6 AM))?
(A) Mars.
(B) Jupiter.
(C) (Both planets.)
(D) (Neither planet.)

Correct answer (highlight to unhide): (B)

If a line is drawn from Earth to the sun, the observer at sunrise (6 AM) is located perpendicular to that line.

Everything below that line would be below the horizon, such that Mars is not visible at sunrise. However, Jupiter would be visible at sunrise, above the sun on the east horizon.

Section 70160
Exam code: quiz02nf0X
(A) : 5 students
(B) : 10 students
(C) : 8 students
(D) : 5 students

Success level: 38% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.88