The tourists want to find a place _ they can have a picnic

The tourists want to find a place __where_ they can have a picnic.那些旅游者想找个他们能野餐的地方.where they can have a picnic做定语从句修饰前面的“a place”；定从自然是有诀窍的,关键要看自己对句子成...可是为什么答案是 which..那我肯定保证答案是错误的！如果想填which的话前面必须有介词in才正确，因为后面的定语从句缺少的是地点状语，如果仅仅填写which的话在句中做什么成分呢？句中主要成分都不缺，只能是状语！希望我的回答你能满意！如果还不确定，请你问问你们老师