Enthuware

This gives {A=[S1:A, S2:A], C=[S3:C]} not {C=[S3:C], A=[S1:A, S2:A]}

I tried it just now and it printed {C=[S3:C], A=[S1:A, S2:A]} as specified in the problem statement.

Regardless of that, in such questions, if you don't see an option like "None of the above", you should pick the best option. In this question, it is option 2.

HTH,
Paul.