Camps are either temporary, that is changed from day to day, or

Camps are either temporary, that is changed from day to day, or they are permanent and may be visited year after year, or they may be used for a few weeks at a time.
【正确答案】：营地可以是临时的，一天一换，也可以是长期的，也许我们每一年都要来或者我们在一段时间内要住上它一两个星期。
【题目解析】：year after year：年复一年。at a time：一次，每次。