Astronomy quiz question: hottest/coolest star?

Astronomy 210 Quiz 5, spring semester 2015
Cuesta College, San Luis Obispo, CA

[Version 1]
Which star is the hottest?
(A) F5 supergiant.
(B) A0 main-sequence star.
(C) M0 red dwarf.
(D) B5 white dwarf.
(E) (There is a tie.)

Correct answer (highlight to unhide): (D)

Using the OBAFGKM spectral type mnemonic, or reading off of an H-R diagram (provided on this quiz, as below), the B5 white dwarf is the hottest star, followed by the A0 main-sequence star, F5 supergiant, and the M0 red dwarf is the coolest.

Section 30674
Exam code: quiz05n36A
(A) : 5 students
(B) : 3 students
(C) : 0 students
(D) : 27 students
(E) : 1 student

Success level: 77% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.70

[Version 2]
Which star is the coolest?
(A) F5 supergiant.
(B) A0 main-sequence star.
(C) M0 red dwarf.
(D) B5 white dwarf.
(E) (There is a tie.)

Correct answer (highlight to unhide): (C)

Section 30676
Exam code: quiz05sOn6
(A) : 0 students
(B) : 1 student
(C) : 39 students
(D) : 5 students
(E) : 1 student

Success level: 85% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.33