Question

It's been a()year since I last saw you A whole B one选哪个请解释

Answer 1

It's been a()year since I last saw you
A whole B one
选哪个请解释
答案是A whole。
It's been a (whole) year since I last saw you
意思是：从上次看到你已经整整一年（过去）了。
这里不能用one，用one变成a one year，与a的意思重叠，有语法错误。
a whole year意思是一整年。