Only wear such clothes-it's really necessary. Please give the answer and analysis.

D. the antecedent contains this, and the attributive clause can only use the relative pronoun as, because as is the subject of the clause, so they can no longer be used.

This ... As means "like ...", where this is an adjective, followed by a noun, and as is a relative pronoun, which leads to an attributive clause, which can serve as a subject, an object and a slogan. Let's just discuss the issues that concern each of us. Let's just talk about the problems related to each of us. (as subject)

Don't read books that you can't understand. Don't read books that you don't understand. (as an object)

He is not as good as he used to be. He is not the man he used to be. (as a predicative)

It is obviously the subject of your sentence.