Respuesta :
Letter A is wrong.
Who substitutes pronouns like he, she or it and whom substitutes him, her and others alike. "He took those pictures?" would have been fine, and so would "Who took those pictures?" Same goes for letter C and D. If you can fit He or She, you should use Who.
B) By whom were those pictures taken?
This is the correct answer. You can see that by rearranging the sentence.
"Those pictures were taken by whom?"
Answer:
B) By whom were those pictures taken?
Explanation:
“Whom” is a pronoun that refers to the object of a verb or a preposition (like “by,” “to” and “from”), meaning that this pronoun does not replace nouns performing the main action, but, instead, it replaces those receiving the main action. Sentence B, then, is using this pronoun correctly because in here it is acting as the object of the preposition “by.”