certain that his invention will lead to the development of production.
| A．That's | B．This is | C．It's | D．What's |
Bears fat stores throughout the summer and fall to have energy enough to last them through their winter sleep.
| A．pack up | B．build up | C．bring up | D．take up |
Half of surveyed in 16 countries say they go first to their closet friend to share their deepest wishes and darkest fears.
| A．these | B．some | C．ones | D．those |
Nothing could be done, he_____ absent.
| A．was | B．being | C．to be | D．be |
He ________ the exam, but he was too careless.
| A．could have passed | B．couldn’t have passed |
| C．must have passed | D．may have passed |
These chairs may look good, but they’re very un-comfortable _____.
| A．to sit on | B．to be sat on | C．sit on | D．sitting on |