________ in the queue for half an hour, Tom suddenly realized that he had left his wallet at home.
| A．To wait |
| B．Have waited |
| C．Having waited |
| D．To have waited |
We are confident that the step the Chinese government has taken to cope with the current crisis is ______ of great significance.
| A．what | B．those | C．that | D．one |
I witnessed the gate of the bank _______ open and many men entering it, but I couldn’t make them out in the darkness.
| A．force | B．be forced | C．forcing | D．being forced |
— I didn’t care about what other people thought about me.
— Well, you ________.
| A．should | B．ought to have | C．would have | D．could |
As a result of __ is now known in physics and chemistry, scientists have been able to make important discoveries in biology and medicine.
| A．it | B．what | C．which | D．that |
These teenagers don’t know much of the world yet; that’s why they are so easily_____.
| A．taken in | B．taken up | C．taken on | D．taken off |