填空题

What should we do to stay healthy One important rule is to exercise often.
The Fisher family try to exercise every day. Mr. Fisher can not exercise in the morning because he must be at his job at exactly seven o’ clock. But he runs every evening. He would rather nm than watch TV. Walter exercises a lot too. He walks to school every day, and after school he plays different sports with his friends. Mrs. Fisher goes to a yoga class twice a week.
The Fishers all feel better now. And they believe you mustn’ t be lazy. You don’ t have to exercise every day. But you should try to get in shape and stay in shape.

How often does Mrs. Fisher go to a yoga class
Mrs. Fisher goes to a yoga class ().