Astronomy current events question: Abell 399 and Abell 401 hot gas bridge

Astronomy 210L, fall semester 2012
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!)

Whitney Clavin, "Planck Spots Colossal Intergalactic Bridge," November 20, 2012
http://www.nasa.gov/mission_pages/planck/news/planck20121120.html

NASA's Planck Space Telescope confirmed the existence of a bridge of hot gas connecting a pair of galaxy clusters by detecting how this gas interacts with:
(A) antimatter.
(B) new star formation.
(C) cosmic background radiation.
(D) dark matter.
(E) super-Jupiters.

Correct answer: (C)

Student responses
Sections 70178, 70186, 70200
(A) : 2 students
(B) : 1 student
(C) : 19 students
(D) : 4 students
(E) : 0 students