Problem: How does the sentence end?

Steven asked Lawrence how to get rid of bamboo taking over, but 
OPTIONS:
- Steven  couldn't remember.
- Lawrence  couldn't remember.
Answer: Lawrence  couldn't remember.

Problem: How does the sentence end?

I want to make this soup using my homemade chicken stock this time instead of water since the 
OPTIONS:
- stock is flavorless.
- water is flavorless.
Answer: water is flavorless.

Problem: How does the sentence end?

Mary started to drill a large hole in Rebecca's front door, because 
OPTIONS:
- Mary was trying to break in.
- Rebecca was trying to break in.
Answer: Mary was trying to break in.

Problem: How does the sentence end?

Don had more wrinkles on his forehead than on his neck because the skin on the 
OPTIONS:
- neck was exposed.
- forehead was exposed.
Answer:
forehead was exposed.