Problem: How does the sentence end?

The windows were replaced by doors to prevent wasting energy, since the 
Answer: doors were well insulated.

Problem: How does the sentence end?

Christopher wasn't a plumber but he knew Matthew was so 
Answer: Christopher called him to fix his sink.

Problem: How does the sentence end?

The violent movie was so graphic that we switched theaters and went to a romance instead.  The 
Answer: movie was something we just hated to see.

Problem: How does the sentence end?

Jessica found that she enjoyed watercolor painting more than oil painting, because the 
Answer:
watercolor paints were cheaper.