请分析下面这句话We must be sure that the scale with which we are com
请分析下面这句话
We must be sure that the scale with which we are comparing our subjects provides a valid comparison.
上面句子里which引导的从句是定语从句还是介词宾语?我看到的ppt说是由with+which引导的定语从句,先行词为the scale,但是我感觉像是介词宾语,希望能解释一下