We haven't discussed yet这是主句,后面跟的是宾语从句,作discuss的宾语
we are going to place our new furniture.从句中,主语是we,谓语是are going to place,宾语是our new furniture.
说明主谓宾都不缺少,那么宾语从句要么由that引导,要么由状语引导,但是用that不合适,表达不出句子的意思.所以判断应该缺少"状语",宾语从句中可以用到的状语有when,where,how.答案里只有where适合
另外,按句意,应该是在“哪里”放家具,所以用where