Astronomy current events question: planet OGLE-TR-113b orbit shrinking

Astronomy 210L, Fall Semester 2010
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!)

Kelly Beatty, "Watching a Planet's Death Spiral?," October 12, 2010
http://www.skyandtelescope.com/news/104782104.html

__________ is evidence that the orbit of planet OGLE-TR-113b is shrinking.
(A) Timing of its transits.
(B) Infrared observations of its hot spot.
(C) Tidal locking.
(D) A massive, yet-unseen companion.
(E) Exchange of tidal energy.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 25 students
(B) : 6 students
(C) : 4 students
(D) : 2 student
(E) : 14 students