[Q]: How does the sentence end?

Erin asked Sarah to be her agent, since 

[A]: Sarah was knowledgeable of the ins and outs of the music business.


[Q]: How does the sentence end?

Samuel pretended to be a ghost while Nick was a witch, so 

[A]: Nick was had the capability to cast a spell.


[Q]: How does the sentence end?

The restaurant sold a lot of steak but not as much salad, as people thought 

[A]:
steak was really delicious.