How long will you stay here A.two and a half month B.two and a half months C.two months and half

问题描述:

How long will you stay here A.two and a half month B.two and a half months C.two months and half
请附带A、B、C三个选项的注解,

B正确.因为half作为“半”的用法时是可数的习惯上加a修饰,所以C错;
month作为可数名词,两个半月是复数,自然地,month后面应加个-s.