Astronomy quiz question: largest star

Astronomy 210 Quiz 4, spring semester 2011
Cuesta College, San Luis Obispo, CA

Which star is largest?
(A) B5 supergiant.
(B) K2 supergiant.
(C) M2 giant.
(D) O5 main sequence star.

Correct answer (highlight to unhide): (C)

Reading off of an H-R diagram (provided on this quiz), the B5 supergiant has a radius a bit less than 100 R_Sun, the K2 supergiant has a radius between 100-1,000 R_Sun, the M2 giant has a radius a little under 100 R_Sun, while O5 main sequence star is approximately 10 R_Sun in radius.

Section 30674
(A) : 7 students
(B) : 3 students
(C) : 20 students
(D) : 8 students

"Success level": 57% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.81
Exam code: quiz04nK4n