[Q]: How does the sentence end?

There are two boys. Donald is interested in girls, while Nick is attracted to boys, which means

[A]: Donald is straight.

[Q]: How does the sentence end?

Rebecca decided to join the Armed Forces, but Rachel had to stay behind to attend school, because

[A]: Rebecca was an adult.

[Q]: How does the sentence end?

Brian suffers a lot from loneliness compared to Brett because

[A]:
Brett still has all of his family.