In those days, we had no phones, so we have to keep in touch _____ writing often.
| A．with | B．of |
| C．on | D．by |
The old man was found on the floor .
| A．lying；dead | B．lying；death |
| C．lying；died | D．laying；dead |
Scientists are convinced ________ the positive effect of laughter _______ physical and mental health.
| A．of; at | B．by; in | C．of; on | D．on; at |
Each of the students，working hard at his or her lessons，to go to university.
| A．hope | B．hopes | C．hoping | D．hoped |
He has devoted all his life ______ the homeless children.
| A．to helping | B．helping | C．to help | D．help |
In the end, Japan and Korea reached the point ___ both sides sat down and had a peaceful talk.
| A．where | B．that | C．when | D．which |