Astronomy current events question: "inside-out" type II supernova

Astronomy 210L, spring 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!)

Janet Anderson and Megan Watzke, "A Star Explodes, Turns Inside-Out," March 29, 2012
http://www.nasa.gov/mission_pages/chandra/multimedia/casa2012.html

Recent images by the NASA's Chandra X-ray Observatory space telescope reveal that a massive star's type II supernova explosion was turned "inside-out" because:
(A) of matter-antimatter reactions.
(B) the finite speed of light.
(C) of a central supermassive black hole.
(D) heavy core elements are outermost.
(E) fusion is still continuing.

Correct answer: (D)

Student responses
Sections 30678, 30679, 30680
(A) : 7 students
(B) : 3 students
(C) : 9 students
(D) : 23 students
(E) : 8 students