Astronomy quiz question: August 2017 partial solar eclipse in San Luis Obispo, CA

Astronomy 210 Quiz 2, spring semester 2017
Cuesta College, San Luis Obispo, CA

A total solar eclipse will occur on August 21, 2017 for many observers in the United States[*]. During this event, observers San Luis Obispo, CA will only see a partial solar eclipse[**], because they will be located in:
(A) the moon's umbra.
(B) the moon's penumbra.
(C) the moon's negative shadow.
(D) Earth's umbra.
(E) Earth's penumbra.

[*] eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2017Aug21Tgoogle.html.
[**] timeanddate.com/eclipse/in/usa/san-luis-obispo?iso=20170821.

Correct answer: (B)

An observer in the moon's penumbra will see a partial solar eclipse, while an observer in the moon's umbra will see a total solar eclipse. (The "negative shadow" refers to the antumbra of the moon.)

Section 30674
Exam code: quiz02n1hT
(A) : 2 students
(B) : 17 students
(C) : 0 students
(D) : 2 students
(E) : 2 students

Success level: 76% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.38

Section 30676
Exam code: quiz02sNoO
(A) : 3 students
(B) : 28 students
(C) : 1 student
(D) : 3 students
(E) : 7 students

Success level: 69% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.64