The correct answer is: She enjoys playing tennis. This is an example of a verb that is followed by a gerund - the 'ing' form of the verb. On the other hand a verb such as 'hope' takes the infinitive form of the verb:
She hopes to visit her parents soon.
Unfortunately, as is the case with irregular verbs, there is no fixed rule for knowing whether a verb takes a gerund or the infinitive. You can improve your understanding by using this gerund or infinitive tool to check and by testing your knowledge with this interactive quiz.

Comments
This lesson is really interesting and useful for my teaching . Thank you very much .