Problem: How does the sentence end?

Mary ended up cleaning Kayla's disgusting room, after that 
OPTIONS:
- Mary demanded payment for doing it.
- Kayla demanded payment for doing it.
Answer: Mary demanded payment for doing it.

Problem: How does the sentence end?

While they were exploring the inside of a huge cave, Betty got lost but luckily Sarah found her before it was too late. 
OPTIONS:
- Betty was rescuing.
- Sarah was rescuing.
Answer: Sarah was rescuing.

Problem: How does the sentence end?

The scientists transferred the water from the bottle into the flask until the 
OPTIONS:
- bottle was empty.
- flask was empty.
Answer: bottle was empty.

Problem: How does the sentence end?

The doctor tried to cure the woman of her cancer an experimental drug, but he was unsuccessful because the 
OPTIONS:
- drug was too strong.
- cancer was too strong.
Answer:
cancer was too strong.