Astronomy quiz question: Milky Way halo new star formation?

Astronomy 210 Quiz 6, fall semester 2012
Cuesta College, San Luis Obispo, CA

There is no new star formation in the halo of the Milky Way because there is/are no __________ left in the halo.
(A) luminous matter.
(B) metals.
(C) interstellar hydrogen.
(D) type II supernova shockwaves.

Correct answer: (C)

New stars form from hydrogen clouds, which are present in the disk of the Milky Way, but not in the halo.

Section 70158
Exam code: quiz06Sl4m
(A) : 3 students
(B) : 4 students
(C) : 20 students
(D) : 3 students

Success level: 66% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.64

Section 70160
Exam code: quiz06n4Rd
(A) : 2 students
(B) : 3 students
(C) : 18 students
(D) : 2 students

Success level: 74% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.43