As soon as I see the word "Which ...", I know that there's a list of choices that goes along with this question, but you decided not to share them. So there's no way for me to help you choose the correct one.
In order to form a proportion with 3/4, you need another fraction (or ratio) that's equal to 3/4 . Look for a fraction whose numerator is 3/4 of its denominator.
