Research shows people with pets in the home visit the doctor less often and experience less sleeping difficulties that ____ without a pet friend.

A. ones    B. those    C. the ones    D.that

該題選B是能理解的。但是，請問為什么the ones不行呢？those與the ones有時可以換用不是嗎？再者，指人時不是更可以用the ones了嗎？