问题
选择题
--- ____ have you been a member of Greener China?
--- For two years.
A．How often
B．How long
C．When
D．How far
答案
答案：B
题目分析：How often多久一次；How long多长，多久；When什么时候；How far多远；根据下文，两年了。可知上文指的是，你成为绿色中国的一员多久了？故选Ｂ。