In _____ preparation for the launching of Shenzhou Ⅶ, scientists need ______ knowledge of weather changes.
| A．the; the | B．a; ∕ | C．∕; a | D．the; a |
I like getting up very early in summer.The morning air is so good ________.
| A．to be breathed | B．to breathe |
| C．breathing | D．being breathed |
—Is Bob still performing?
—I'm afraid not.He is said ________ the stage already as he has become an official.
| A．to have left | B．to leave |
| C．to have been left | D．to be left |
The flu is believed ________ by viruses that like to reproduce in the cell inside the human nose and throat.
| A．causing | B．being caused |
| C．to be caused | D．to have caused |
________ the meeting himself gave them a great deal of encouragement.
| A．The president will attend |
| B．The president to attend |
| C．The president attended |
| D．The president's attending |
—They are quiet，aren't they?
—Yes.They are accustomed ________ at meals.
| A．to talk | B．to not talk |
| C．to talking | D．to not talking |