Problem: How does the sentence end?

Benjamin always smells nice but Nelson doesn't because 
OPTIONS:
- Benjamin  is an expert at keeping things clean.
- Nelson  is an expert at keeping things clean.
Answer: Benjamin  is an expert at keeping things clean.
sentence: When opening up about their crushes, Kenneth sighed at Jeffrey because  OPTIONS:
- Kenneth forgot who their crush was.
- Jeffrey forgot who their crush was.
complete: Jeffrey forgot who their crush was.
Lindsey begged Rebecca to try her homemade Pho soup that she had made.  
OPTIONS:
- Lindsey was disgusted.
- Rebecca was disgusted.
Rebecca was disgusted.
Input: Continue writing.

Christopher practiced fire safety and Derrick did not, so 
OPTIONS:
- Christopher remained calm when the fire alarm at the office building went off.
- Derrick remained calm when the fire alarm at the office building went off.

Continued: Christopher remained calm when the fire alarm at the office building went off.
Story needs to be completed:
The stones that I found at the beach were worse than the rocks I found earlier, because the 
OPTIONS:
- stones were common.
- rocks were common.

My choice:
stones were common.
Problem: How does the sentence end?

A boy in a house tries to put a big book on a shelf built for paperbacks. The book falls to the ground because the 
OPTIONS:
- shelf is too narrow.
- book is too narrow.
Answer:
shelf is too narrow.