Only take such clothes -- really necessary.请给答案和分析.

D.先行词含有such,定语从句引导词只能用关系代词as,由于as在从句中作主语,因此不能再用they.
such...as意为“像.一样.”其中such是形容词,后接名词,as是关系代词,引导定语从句,在定语从句中可充当主语、宾语、标语.如：Let's discuss only such questions as concern every one of us.我们只谈与我们每个人都有关的问题吧.(as做主语)
Don't read such books as you can't understand.不要看你们看不懂的书.（as作宾语）
He isn't such aman as he used to be.他已经不是过去那个样子了.(as作表语）
在你的句子中as 显然是作主语的