Astronomy current events question: confirmation of K2-155 "super-Earths"

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!)

News release, "15 New Planets Confirmed Around Cool Dwarf Stars" (March 12, 2018)
titech.ac.jp/english/news/2018/040761.html

Three "super-Earth" planets orbiting red dwarf K2-155 were among 15 exoplanets discovered by NASA's Kepler space telescope, and later confirmed by:
(A) gravitational wave detectors.
(B) computer simulations.
(C) ground-based telescopes.
(D) radar signals.
(E) searches by volunteers.

Correct answer: (C)

Student responses
Sections 30679, 30680
(A) : 9 students
(B) : 9 students
(C) : 15 students
(D) : 5 students
(E) : 2 students