Question

Which personal pronoun correctly completes the sentence? __________ and Martha both dance very well. A. Hers B. Her C. She

Answer 1

Answer: The right answer is the C. She.

Explanation: Just to elaborate a little on the answer, it can also be added that the pronoun her is the objective form of she—not the possessive—and it could have been used if the sentence had read: "I saw Martha and her dancing," for instance. In addition, hers—which is the possessive form of she—could have been used if the sentence had read: "I saw Martha dancing. Hers is a very unconventional style of dancing," just to provide you with an example. Therefore, the pronoun she is the one that correctly completes the sentence, since it is one of the subjects of the verb.      

Answer 2

The personal pronoun that is correctly complete the sentence is : C. she

The other options are only use when there is a possessive form, which make C became the most possible choice for you

hope this helps