Astronomy current events question: TRAPPIST-1 planet compositions

Astronomy 210L, spring semester 2018
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!)

Simon Grimm and Brice-Olivier Demory, "What the TRAPPIST-1 Planets Could Look Like" (February 5, 2018)
unibe.ch/news/media_news/media_relations_e/media_releases/2018/media_releases_2018/what_the_trappist_1_planets_could_look_like/index_eng.html

All seven exoplanets orbiting the star TRAPPIST-1 may be mostly composed of rock and some covered with water, as determined from:
(A) Hubble Space Telescope images.
(B) reflected radio waves.
(C) interferometry.
(D) computer models.
(E) gravitational lensing.

Correct answer: (D)

Student responses
Sections 30679, 30680
(A) : 19 students
(B) : 4 students
(C) : 4 students
(D) : 9 students
(E) : 2 students