All of us still remember the terrible earthquake that ________Tangshan twenty years ago.
5. Honest ________, though unpleasant to the ear, induces good conducts. (prov.)
6. We haven't seen each other for _______, though we are in the same city.
7. Our older generation used to advise us not to build ____ in the air, but that’s not realistic at all.
8. Usually passengers are required to arrive at _____ one hour before ______ takes off.
9. Which of the following is not a flying machine?