Astronomy current events question: TRAPPIST-1 exoplanets discovery

Astronomy 210L, spring semester 2017
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, Sean Potter, Elizabeth Landau, "NASA Telescope Reveals Largest Batch of Earth-Size, Habitable-Zone Planets Around Single Star" (February 22, 2017)
nasa.gov/press-release/nasa-telescope-reveals-largest-batch-of-earth-size-habitable-zone-planets-around

NASA's Spitzer space telescope observed seven Earth-size planets in the TRAPPIST-1 system as they __________ their star.
(A) escaped from.
(B) gravitationally wobbled.
(C) crossed in front of.
(D) tidally locked onto.
(E) reflected light from.

Correct answer: (C)

Student responses
Sections 30679, 30680
(A) : 3 students
(B) : 4 students
(C) : 10 students
(D) : 5 students
(E) : 8 students