Astronomy current events question: Earth core formation

Astronomy 210L, fall semester 2013
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!)

Simon Redfern, "New Ideas for How Earth Core Formed," October 11, 2013
http://www.bbc.co.uk/news/science-environment-24454138

Stanford University researchers analyzed __________, providing evidence of how iron may have flowed inwards to form Earth's core.
(A) materials squeezed between diamond anvils.
(B) earthquakes under iron-rich volcanoes.
(C) underground mine temperatures.
(D) ancient sample radioactivity.
(E) local fluctuations in gravity.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 35 students
(B) : 6 students
(C) : 3 students
(D) : 4 students
(E) : 4 students