Our duty is to ______ their country against both domestic and foreign enemies’ attack.

(2013·厦门质量检测)Some fruits are so easily harvested in this area that they are never of great________.

In order not to _____ in front of the audience, the speaker spent many hours preparing his speech. 

The part that China _________in the international affairs _________ in the international society.

The government has been under growing pressure to ______ the causes of air pollution as smog frequently smothers the country's large cities．