I always regret not harder when I was young .
| A．studying | B．having studied | C．to study | D．to have studied |
19．China has warned America that it_____be responsible for its arms sale to Taiwan.
| A．can | B．may | C．will | D．Shall |
18．An explosion in a coal mine in Heilongjiang on Nov. 21, 2009______at least 106 workers dead.
| A．promoted | B．kept | C．left | D．Created |
17．—Hi, Nancy, I didn't know you had come back. So have you graduated from college?
—Yes. I______French for 5 years in Nanjing.
| A．have studied | B．studied | C．had studied | D．am studying |
16．－What about going abroad?
－Great, but I never expected______a chance for me before.
| A．there to be | B．there being | C．there is | D．there to have |
15．The population of China_______to many times what it was in 1949, and most of its population
farmers.
| A．have grown; are | B．have grown; is |
| C．has grown; is | D．has grown; are |