I will start out with the problems in the original sentence.
declared A B is an idiom. You don't need 'as' between A and B. That eliminates A, B, and E.
Further, focus on parallelism.
Supreme Court declared ..., and ruling that....
For it to be parallel we should have ruled to be parallel with declared but we have ruling in the non-underlined portion. Since ruling is mentioned in the non-underlined part, it can work only as a verb-ing modifier of the previous clause. So sentence of the structure should be as follows.
Supreme court declared something unconstitutional, ruling that...
In this way, modifier "ruling that..." describes,modifies or give further information on what SC declared.
So 'and' before ruling is wrong as ruling... is not really parallel with declared as explained above. This eliminates A and B.
E is wrong as it doesn't have a main clause. "when SC declared..." is an dependent clause. So a dependent clause followed by a modifier "ruling that...". We should have atleast one independent clause in a sentence.
D is wrong as the modifier should make sense with the subject of the main clause it modifies. Here ruling is done by SC so subject of the main clause should be SC and the minimum wage. In option C, we do have SC as the subect of the main clause therefore
C is the correct option.Hope it helps