Complete the question with the correct question word: ¿ es la hermana de marcos? a. dónde b. cuáles c. quién d. qué

¿ es la hermana de Marcos?

Translation:

[Blank] is Marcos' sister?

The options

A. Dónde - where

B. Cuáles - which ones

C. Quién - who

D. Qué - what

Option B can be eliminated because it is plural, while the verb (is) is singular.

Option D can safely be eliminated because it doesn't make sense to ask "what is his sister?" in this manner under any circumstances.

It might seem like option A, dónde, is the correct answer, however, when asking where someone is, estar is used, rather than ser.

You would say ¿Dónde esta la hermana de Marcos?

The leaves option C, which is correct. The question is Who is Marcos' sister?

C. Quién