问题补充：
- do you go back to your hometown to visit your grandparents?
- Twice a year: Usually at Mid-Autumn festival and during the Chinese New Year.
A. How long
B. How often
C. How much
D. How many
答案：
A. How long
(答案→)B. How often
C. How much
D. How many
解析：
试题分析: 句意：你多久回一次家乡看望祖父母？一年两次。通常是在中秋节和春节期间。How long多久， How often多久一次，How much 多少， How many多少；根据Twice a year一年两次，可知是对频率进行提问，故选B.
