First: It’s called the “correct answer”, not the “true answer”.
Since the verb is “was”, which is singular, it can’t be A or B.
D makes no sense, so your only option is C.
“Neither” has the meaning “not the one nor the other of two people or things”, but
occasionally that rule is broken.
The correct answer would have been “none”, but the person who designed the test obviously had a bad day.