---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：交际用语。疑问词how often是对频率的提问，只有B项符合题意，故答案为B。