第二节 完成句子（共5小题；每小题2分，满分10分）
1. The two countries were then ________ ________（交战）. People lived a hard life.
2. The letters PLA __________ __________ （代表）the People’s Liberation Army.
3. To be a good learner, you must _________ _________ ________ _______（充分利用）the library books, newspapers and magazines.
4. They were both punished ______ _______ ________ ________（由于……的结果）smoking.
5. He likes to ________ ________ _______（拿……开玩笑） me because we are friends.