A is incorrect.
http://leo.stcloudstate.edu/punct/colon.html
and
Do not use a colon immediately after a verb.
A) His chief complaints were: impotence, flatulence, and fatigue.
B) His chief complaints were: Impotence, Flatulence, and Fatigue.
C) His chief complaints were impotence, flatulence, and fatigue.
My answer is A
http://leo.stcloudstate.edu/punct/colon.html
and
Do not use a colon immediately after a verb.
In this sentence, the items in the list of chief complaints (impotence, flatulence, and fatigue) are correctly punctuated, spaced, and capitalized.
- Punctuation: The items in the list are separated by commas, which is the standard punctuation for listing multiple items.
- Spacing: There is a space after the colon (:) that separates the introductory phrase "His chief complaints were" from the list.
- Capitalization: The list items are not capitalized unless they are proper nouns. Since "impotence," "flatulence," and "fatigue" are common nouns, they are correctly written in lowercase.
So, Sentence A is the correct choice. Well done!