____some doubt among scientists about the cause of cancer.
| A．It exists | B．There exists | C．There is existing | D．It is existing |
The work he paid special attention _____ to nothing.
| A．came | B．to come |
| C．to coming | D．to came |
The life he is now used _____ quite different from ours.
| A．is | B．to be | C．to being | D．to is |
The old house we paid a visit _____ at the top of the hill.
| A．standing | B．to stand |
| C．to standing | D．to stands |
Nothing that he suggested _____ to be of any use.
| A．prove | B．proved | C．proving | D．to prove |
What the boy enjoys _____ to have a room of his own.
| A．being | B．to be | C．is | D．are |