12. My sister ______ (visit) our grandma every weekend.

Explanation:

The phrase 'every weekend' indicates a recurring or habitual action, which is expressed using the present simple tense.

Solution:

For the third person singular subject 'My sister', the present simple tense adds '-s' to the base form of the verb.

1. Subject: My sister (third person singular)
2. Main verb: visit + s = visits

Answer: visits