Astronomy current events question: synestia formation of Earth and the moon?

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!)

Andy Fell, "How the Moon Formed Inside a Vaporized Earth Synestia" (February 28, 2018)
ucdavis.edu/news/how-moon-formed-inside-vaporized-earth-synestia/

A recent theory proposes that both Earth and the moon formed within a synestia, which is a donut-shaped cloud of __________ formed after the collision of two planet-sized objects:
(A) vaporized rock.
(B) radioactive asteroids.
(C) dark matter.
(D) antimatter.
(E) neutrinos.

Correct answer: (A)

Student responses
Sections 30679, 30680
(A) : 24 students
(B) : 1 student
(C) : 0 students
(D) : 0 students
(E) : 2 students