Left ____ in the reading room alone quite by accident, the boy felt nervous.
| A．locking | B．having locked |
| C．to lock | D．locked |
In the past five years China ________ great _________.
| A．made, progress | B．has made, progresses |
| C．made, progresses | D．has made, progress |
They talked for about an hour of things and persons _____ they remembered in the school.
| A．which | B．that | C．who | D．whom |
Don’t be in a hurry. We are supposed ____________ this problem step by step.
| A．solving | B．to solving | C．to solve | D．solve |
_________you have a rich knowledge of Chinese history, try acting as a guide for these foreign visitors.
| A．Unless | B．Though | C．Now that | D．Ever since |
The school ______ my sister studies at is far from here.
| A．where | B．that | C．at which | D．in which |