Astronomy current events question: Abell 2744 "ghost light"

Astronomy 210L, fall semester 2014
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!)

Felicia Chou, Ray Villard, and Mireia Montes, "Hubble Sees 'Ghost Light' From Dead Galaxies," (October 30, 2014)
http://hubblesite.org/newscenter/archive/releases/2014/43/full/

NASA's Hubble Space Telescope picked up infrared "ghost light" in galaxy cluster Abell 2744 from stars:
(A) on a collision course with each other.
(B) with extreme gravitational redshifts.
(C) ejected from broken-apart galaxies.
(D) that exploded as type II supernovae.
(E) consumed by a supermassive black hole.

Correct answer: (C)

Student responses
Sections 70178, 70186
(A) : 2 students
(B) : 3 students
(C) : 23 students
(D) : 5 students
(E) : 4 students