Astronomy current events question: KIC 05807616 "cell-division" planets

Astronomy 210L, spring 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!)

Lisa Grosmann, "The Planets That Formed by Cell Division," April 2, 2012
http://www.newscientist.com/article/dn21659-astrophile-the-planets-that-formed-by-cell-division.html?full=true

Two planets that may have split from a single planet orbiting the star KIC 05807616 were discovered from:
(A) variations in reflected light as they orbit their star.
(B) heat released while engulfed by the star's outer layers.
(C) brown dwarf radio emissions.
(D) gravitational tidal forces separating their cores.
(E) magnetic field disturbances.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 13 students
(B) : 5 students
(C) : 4 students
(D) : 0 students
(E) : 3 students