Astronomy current events question: young Cepheids in Milky Way bulge

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!)

Istvan Dékány, Dante Minniti, Daniel Majaess, Richard Hook, "VISTA Discovers New Component of Milky Way" (October 28, 2015)
eso.org/public/usa/news/eso1542/

A group of stars near the center of the Milky Way observed by the European Southern Observatory's VISTA telescope are very young in age, based on their:
(A) Doppler shifts.
(B) rapid orbits.
(C) still-forming planets.
(D) pulsation periods.
(E) absorption spectra.

Correct answer: (D)

Student responses
Sections 70178, 70186
(A) : 4 students
(B) : 2 students
(C) : 3 students
(D) : 19 students
(E) : 6 students