Choose the appropriate variant. Mary ... at the moment.

The correct answer is 'isn't swimming'. Explanation: The phrase 'at the moment' indicates that the action is happening right now, so we need to use the Present Continuous tense. The Present Continuous is formed using 'is/am/are + verb-ing'. Since the subject is 'Mary' (singular), we use 'is'. Thus, the correct option is 'isn't swimming'. Answer: isn't swimming