They spent a couple of days and nights on the far

They spent a couple of days and nights on the farm of ( ) could be considered as a very poor family. 为什么这里面填what?填which不可以吗？求解释?

what连接前后两个部分，既是of的宾语，也引导后面的句子
如果是which只能起其中的一个作用，which引导从句的话前面需要有先行词
句子可以改为they spent a couple of days and nights on the farm of the situation（可以用一个更适合的词，暂时没想到） which would be considered a poor family.

wha????????????????????????