—What should I do, doctor?
—___healthy, you should take more exercise.
| A．To keep | B．Keep | C．Keeping | D．Kept |
John didn’t go to bed ______he finished his homework.
A.until B.after C.while
It took him half an hour _____ the work.
A.doingB.to do C.did
The teachers are very friendly ______their students.
A.to B.at C.on
His shoes are ___dirty ____he has to wash them .
A.too, to B.so, that C.enough, that
She missed the bus,_____she had to walk home.
A.so B.but C.because