Astronomy current events question: possible origin of Neptune's moon Hippocamp

Astronomy 210L, spring semester 2019
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!)

Ray Villard, Mark Showalter, and Jack Lissauer, "Tiny Neptune Moon May Have Broken from Larger Moon" (February 20, 2019)
solarsystem.nasa.gov/news/854/tiny-neptune-moon-may-have-broken-from-larger-moon/

Researchers propose that Neptune's smallest moon, Hippocamp, may be a fragment produced when a larger moon, Proteus:
(A) collided with a comet.
(B) flipped its magnetic poles.
(C) formed from Neptune's rings.
(D) had active cryovolcanoes.
(E) was pulled in from the asteroid belt.

Correct answer: (A)

Student responses
Sections 30679, 30680
(A) : 33 students
(B) : 0 students
(C) : 2 students
(D) : 1 student
(E) : 2 students