Astronomy current events question: "Planet Nine" evidence?

Astronomy 210L, spring semester 2016
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!)

Kimm Fesenmaier, "Caltech Researchers Find Evidence of a Real Ninth Planet" (January 20, 2016)
caltech.edu/news/caltech-researchers-find-evidence-real-ninth-planet-49523

Evidence that the outer solar system may have a previously undiscovered giant planet in an elongated orbit is based on:
(A) mathematical models.
(B) rogue asteroid compositions.
(C) solar flare fluctuations.
(D) analyzing old photos.
(E) Egyptian hieroglyphs.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 24 students
(B) : 10 students
(C) : 8 students
(D) : 3 students
(E) : 0 students