_____to nuclear radiation, even for a short time , may produce variants(变异体) of genes in human bodies.
| A．Being exposed | B．Having expose |
| C．Exposed | D．After being exposed |
I _____ in London for many years, but I’ve never regretted my final decision to move back to China.
| A．have lived | B．was living | C．lived | D．had lived |
Ladies and gentlemen, please fasten your seat belts. The plane________.
| A．takes off | B．is taking off | C．has taken off | D．took off |
Look at the timetable. Hurry up! Flight 4026 ____ off at 18:20.
| A．will be taken | B．took | C．takes | D．has taken |
—Shall I help you, sir?
—I appreciate ____ if you do me the favor to pack the luggage.
| A．/ | B．that | C．you | D．it |
Helping others is a habit, ___ you can learn even at an early age.
| A．it | B．that | C．one | D．those |