-----Did you find the missing couple in the mountain yesterday?
-------No, but we _ to get in touch with them ever since.
A have tried
B. had tried
C. have been trying
D. had been trying
6. We haven't seen each other for _______, though we are in the same city.
| A．eras | B．millennium | C．epoch | D．Ages |
7. Our older generation used to advise us not to build ____ in the air, but that’s not realistic at all.
| A．attics | B．castles | C．building | D．Rostrums |
8. Usually passengers are required to arrive at _____ one hour before ______ takes off.
| A．airport; aircrafts | B．the airport, aircraft |
| C．an airport, a aircraft | D．the airport, the aircraft |
9. Which of the following is not a flying machine?
| A．plane | B．aircraft | C．kite | D．space ship |
10. As middle school students, raising pet ______ all day long is a sheer waste of time.
| A．beasts | B．creatures | C．cat | D．Dog |