Question

It___ten years since he left the army. A.is B.has C.will D.was 这题应该怎么选？求详细的解答。谢谢。

Answer 1

正确答案是A，这里也可以填has been。is比较口语化,而填has been比较正式一点，因为句子中有since引导一个过去时的句子，主句应该用现在完成时。两者都是正确的，可以互相转换。该句子可以做如下转换：
He left the army ten years ago.
=It has been ten years since he left the army.
=It is ten years since he left the army.
=Ten years has passed since he left the army.

Answer 2

这题的答案应该要填入 has been，可是不在选项内。可以去挑战老师，题目有误。

Answer 3

(A) has been 在这里可用is 代替

Answer 4

支持楼上的说法。