[Q]: How does the sentence end?

Rebecca had to ask Elena if they needed to cheat, because

[A]: Elena had not studied the night before.

[Q]: How does the sentence end?

Since Matthew studied physics while Ian studied English,

[A]: Ian knew a lot about English literature.

[Q]: How does the sentence end?

Randy learned to fish from Derrick, because

[A]:
Derrick was a professional with years of experience.