b. She buys presents at Christmas. She buys presents once a year. c. They go to French classes on Tuesdays and Thursdays. They go to French classes twice a year. d. I see my grandparents at Christmas, Easter and in the summer. I see my grandparents three times a year.
Объяснение:
1 раз - once; дважды - twice;
начиная со слова трижды, после цифры пиши слово times. Three times, four times, five times, ten times ...