The correct option is C so has his sister
Let’s examine the sentence: “John has written a novel and ____ .” When we see the options, we understand that the blank needs a clause reiterating the fact given in the first clause of the sentence but for John’s sister. Hence, the adverb ‘so’ would be used to express the similarity of fact in both the clauses. The adverb ‘so’ means ‘to the same extent’ when used in comparisons. Now, the tense would also be the same and to emphasize the fact stated in the first clause, same helping verb as used in the first clause would be taken here after ‘so.’ As Option C fulfills these conditions, it is the correct answer. Other options cannot be used as they would make the sentence meaningless.