Astronomy quiz question: giant energy source

Astronomy 210 Quiz 5, fall semester 2011
Cuesta College, San Luis Obispo, CA

The energy source in the core of a giant is:
(A) hydrogen fusion.
(B) gravitational contraction.
(C) fusion of elements heavier than hydrogen.
(D) radioactive decay.
(E) (Does not produce energy.)

Correct answer: (C).

A giant is a medium-mass star that has converted all of the hydrogen in its core to helium at the end of its main sequence lifetime. After a brief intermediate stage where energy is produced by hydrogen fusion in a shell surrounding its core, energy is then produced in the core by the fusion of helium into carbon.

Section 70158
Exam code: quiz05SpRn
(A) : 18 students
(B) : 0 students
(C) : 13 students
(D) : 0 students
(E) : 2 students

Success level: 45% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.22