Giải chi tiết giúp mình ạ 

The doctor says Jenny can come home Friday if she continue ___.

A. to improve

B. to improving

C. improve

John forced himself ___.

A. improve

B. to improving

C. improving

Peter should ___ this course to finish his study.

A. stop

B. continue

C. start

Sara has had ___ problems with this car.

A. continue

B. continuing

C. continual

Anna was angry because John ___ interrupted her.

A. continual

B. continually

C. continued