Astronomy quiz question: March 23, 2016 penumbral lunar eclipse

Astronomy 210 Quiz 3, spring semester 2016
Cuesta College, San Luis Obispo, CA

Before sunrise on the morning of March 23, 2016, the moon will pass inside Earth's penumbra for observers in San Luis Obispo, CA[*]. These observers will see:
(A) a dark shadow across part of a full moon.
(B) a very, very dark brown-red full moon.
(C) a full moon slightly dimmer than usual.
(D) only part of the sun blocked by a new moon.
(E) the entire sun blocked by a new moon.
(F) a new moon not large enough to entirely block the sun while in front of it.

[*] timeanddate.com/eclipse/lunar/2016-march-23.

Correct answer (highlight to unhide): (C)

When the moon is completely within Earth's penumbra, it is still illuminated by some of the sun's light, and will be only slightly dimmer (but usually not noticeably dimmer, to the naked eye) than a regular full moon.

(The full moon would appear a very, very dark brown-red during a total lunar eclipse, when it is completely within Earth's umbra; and the full moon would have a dark shadow across part of it (assuming that is the extent of what is covered on the full moon) during a partial lunar eclipse, when only part of it (at most) would be within Earth's umbra.)

(The entire sun would be blocked by a new moon during a total solar eclipse, as seen by an observer located under the moon's umbra; only part of the sun would be blocked by a new moon (assuming that is the extent of what is covered by the moon) during a partial solar eclipse, where the observer is in the moon's penumbra; and a new moon not large enough to entirely block the sun while in front of it would be seen during an annular solar eclipse, where the observer is in the moon's antumbra (in this class, called the "negative shadow").)

Section 30674
Exam code: quiz03n0V4
(A) : 5 students
(B) : 5 students
(C) : 1 student
(D) : 5 students
(E) : 3 students
(F) : 1 student

Success level: 8% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.17

Section 30676
Exam code: quiz03s4rA
(A) : 12 students
(B) : 9 students
(C) : 12 students
(D) : 9 students
(E) : 3 students
(F) : 3 students

Success level: 28% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.36