Astronomy current events question: most-massive black hole?

Astronomy 210L, fall semester 2012
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!)

Remco van den Bosch, Arjen van der Wel, Markus Pössel, "Black Hole Upsets Galaxy Models," November 29, 2012
http://www.mpg.de/6648360/black-hole-galaxy-models

According to researchers from the Max Planck Institute for Astronomy, the central black hole in galaxy NGC 1277 may be the most massive yet discovered, as determined by measuring:
(A) spectra of surrounding stars.
(B) emitted x-ray flares.
(C) gravitational lensing.
(D) pulsar radio beams.
(E) space-time distortions.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 12 students
(B) : 7 students
(C) : 6 students
(D) : 6 students
(E) : 3 students