Question:
Ryan made Nick recite mathematical formulas for the test, because

Answer:
Continue the sentence -- Ryan is his math tutor.

Question:
Rebecca called Amy on Skype but didn't get an answer.

Answer:
Continue the sentence -- Rebecca was dejected about missing them.

Question:
The company built the structure using steel but not iron because the

Answer:
Continue the sentence -- iron was costly.

Question:
Tim went to the store for potatoes but got sweet potatoes instead because the

Answer:
Continue the sentence -- sweet potatoes looked better.