Lana had great fun swimming in the river.改为同义句Lana _____ a great time when she _____ in the rivers.应填：had swam解析：have fun = have a great time 玩得开心swam 为swim 的过去式...为什么是swam而不是swims呢？主句和从句应保持一致 主句用了 have 的过去式 had