[Q]: How does the sentence end?

The serum Betty was using doesn't work as well as Amy's because

[A]: Betty shopped at a discount store.

[Q]: How does the sentence end?

Matthew knew that their ring contained real diamonds but Derrick did not because

[A]: Derrick was a novice on gemstones.

[Q]: How does the sentence end?

The customer wanted to buy the cardigan but settled on the belt because the

[A]:
belt was cheap.