Astronomy current events question: Eta Carinae supernova imminent?

Astronomy 210L, Fall Semester 2009
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!)

Kelly Beatty, "A Rogue Star Going Wild?," November 26, 2009
http://www.skyandtelescope.com/news/home/75160377.html

What observations by the Hubble Space Telescope Imaging Spectrograph indicate that the stars in the binary star system Eta Carinae may soon explode as type II supernovas?
(A) Size of both stars have suddenly collapsed.
(B) Size of both stars have increased, merging them together.
(C) Increase in x-rays where their outflowing winds collide.
(D) Neighboring star's supernova shockwave will soon hit Eta Carinae.
(E) Orbits of both stars are spiraling even closer.

Correct answer: (C)

Student responses
Sections 70178, 70186, 70200
(A) : 9 students
(B) : 11 students
(C) : 27 students
(D) : 4 students
(E) : 11 students