Astronomy current events question: extragalactic "hypervelocity" stars?

Astronomy 210L, fall 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!)

Scott Sheppard, "New Extremely Distant Solar System Object Found During Hunt for Planet X" (October 2, 2018)
esa.int/Our_Activities/Space_Science/Gaia/Gaia_spots_stars_flying_between_galaxies

The European Space Agency's Gaia spacecraft discovered a set of "hypervelocity stars" that may have:
(A) escaped from black holes.
(B) ages much younger than the sun.
(C) come from outside the Milky Way.
(D) nearly collided with sun in the past.
(E) triggered solar system planet formation.

Correct answer: (C)

Student responses
Sections 70178, 70186
(A) : 5 students
(B) : 1 student
(C) : 11 students
(D) : 3 students
(E) : 3 students