[Q]: How does the sentence end?

I tried to fit the paper under the door, but it wouldn't go because the 

[A]: paper was too thick.


[Q]: How does the sentence end?

The actor tried to use the book to develop a new personality but the 

[A]: book was too complicated.


[Q]: How does the sentence end?

Robert trusted Leslie to broker his money online because, between the two of them, 

[A]:
Robert was the amateur investor.