There are two main sets of Games—the Winter and the Summer Olympic Games and both are held every four years on a regular basis . 运动会主要有两种；夏季奥运会和冬季奥运会。这两种会都是四年举行一次。 【观察思考】 Usually, medicine should be taken every four hours/every fourth hour. 一般说来，每隔四小时吃一次药。 2）Some of you go back home every two weeks. 你们中一些人每两星期回家一次。