Astronomy current events question: globular cluster Terzan 5 star age groups

Astronomy 210L, fall semester 2016
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!)

Liz Kruesi, "Astronomers Find Fossil Stars from the Beginning of the Galaxy" (September 9, 2016)
astronomy.com/news/2016/09/astronomers-find-fossil-stars-from-the-beginning-of-the-galaxy

Globular cluster Terzan 5 contains two different age groups of stars, as determined by analysis of the stars':
(A) brightnesses and colors.
(B) dark-matter content.
(C) speeds and motions.
(D) supernovae formation rate.
(E) gravitational waves.

Correct answer: (A)

Student responses
Sections 70178, 70186
(A) : 23 students
(B) : 0 students
(C) : 3 students
(D) : 3 students
(E) : 1 student