Problem: How does the sentence end?

The professor gave Nick but not Logan an A because 
OPTIONS:
- Nick showed extensive knowledge of the periodic table of elements.
- Logan showed extensive knowledge of the periodic table of elements.
Answer: Nick showed extensive knowledge of the periodic table of elements.

Problem: How does the sentence end?

The art store sold lots of canvas but very few frames, as 
OPTIONS:
- canvas were so expensive.
- frames were so expensive.
Answer: frames were so expensive.

Problem: How does the sentence end?

Jeffrey was the receptionist for the company while Derrick was the data clerk because 
OPTIONS:
- Jeffrey disliked to work with people.
- Derrick disliked to work with people.
Answer: Derrick disliked to work with people.

Problem: How does the sentence end?

Wanting to be comfortable, the woman placed a pillow on the sofa because the 
OPTIONS:
- pillow was stiff.
- sofa was stiff.
Answer:
sofa was stiff.