Astronomy current events question: Alpha Centauri B Earth-mass extrasolar planet

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!)

Xavier Dumusque et al., "Planet Found in Nearest Star System to Earth," October 16, 2012
http://www.eso.org/public/news/eso1241/

The European Southern Observatory's La Silla Observatory in Chile discovered an Earth-mass planet by observing __________ the nearby star Alpha Centauri B.
(A) reflected light from.
(B) its gravitational pull on.
(C) the eclipses of.
(D) the parallax of.
(E) a dusty disk surrounding.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 10 students
(B) : 30 students
(C) : 8 students
(D) : 5 students
(E) : 3 students