Astronomy current events question: diamond planet

Astronomy 210L, fall semester 2011
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!)

Tammy Plotner, "Star Transforms Into A Diamond Planet," August 25, 2011
http://www.universetoday.com/88449/star-transforms-into-a-diamond-planet/

A planet made of diamond orbiting pulsar PSR J1719-1438 was discovered by analyzing:
(A) the planet's surface hardness.
(B) pulsar light passing through the planet.
(C) pulsar radio signal variations.
(D) carbon-rich vapor trails.
(E) radioactive micrometeorite diamonds.

Correct answer: (C)

Student responses
Sections 70178, 70186, 70200
(A) : 2 students
(B) : 16 students
(C) : 27 students
(D) : 8 students
(E) : 1 student