—How often do you see your grandparents?—.A. Five days B. Once a month C. In a week

问题补充：

—How often do you see your grandparents?

—.

A. Five days B. Once a month C. In a week

答案：

解析：句意：你多久去看望一次你的祖父母？一个月一次。A五天B一月一次C一周以后，根据句意，冠词B