-are you staying there? -Just for two days.A. How often B. When C. How long

问题补充：

-are you staying there? -Just for two days.

A. How often B. When C. How long

答案：

解析：How often多久一次；When什么时候；How long多长。根据下文答语，只有两天。可知选C，你打算在这呆多长时间？