Astronomy current events question: oldest known Milky Way stars

Astronomy 210L, fall semester 2015
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)

Charles Q. Choi, "These Ancient Stars May Be the Oldest Ever Seen in the Milky Way" (November 11, 2015)
space.com/31083-oldest-stars-milky-way-galaxy.html

The Australia National University's SkyMapper telescope discovered the oldest known stars in the Milky Way, based on their:
(A) lack of metals.
(B) erratic orbits.
(C) type II supernova explosions.
(D) gravitational redshifts.
(E) dark matter content.

Correct answer: (A)

Student responses
Sections 70178, 70186
(A) : 13 students
(B) : 1 student
(C) : 4 students
(D) : 3 students
(E) : 1 student