The correct option is D As
Option D is correct for the conjunction here connects the two clauses of the sentence. When used as conjunction, ‘as’ is used to indicate by comparison the way that something happens or is done. In this sentence, ‘as’ is referring to leaving the things in their original way. So, ‘as’ would be used here. Option A cannot be used as the sentence does not require a verb. Option B cannot be used as ‘so’ is used to indicate consequence, purpose, addition, degree, agreement or confirmation. Hence, the usage of ‘so’ does not fulfill the requirement of the sentence of connecting its two clauses. Option C cannot be used as ‘like’ is used for showing comparison and this is also not the need of this sentence.