[Q]: How does the sentence end?

Samuel failed their final exams while Brian passed them, so 

[A]: Samuel needed to retake their classes in summer school.


[Q]: How does the sentence end?

The students took a longer time calculating the physics problem than the engineering problem since the 

[A]: physics problem was rather complex.


[Q]: How does the sentence end?

Derrick took much inspiration from the life story of Nick, so 

[A]:
Nick received from him a letter.