Rachel was a much better cook than Mary because
OPTIONS:
- Rachel couldn't even boil eggs correctly.
- Mary couldn't even boil eggs correctly.
Mary couldn't even boil eggs correctly.

Laura was a frugal shopper whereas Christine was the opposite.
OPTIONS:
- Laura could never buy that much stuff at once.
- Christine could never buy that much stuff at once.
Laura could never buy that much stuff at once.

Doctors usually prefer to give patients vaccines instead of medications because the
OPTIONS:
- vaccines are more certain.
- medications are more certain.
vaccines are more certain.