Question

It's four years since Mike ____ to Tibet. A.has been B. is coming C.will come D.came

答案是D，为什么不是A呢

Answer 1

你好：
D.came
全翻译：自从麦克来到台北，已经四年了。
Since sb. did ...这里本身就决定了是过去式哦
希望我的回答对您有帮助，祝好！

Answer 2

你好
句型：
It is +一段时间+since...意思是“自......发生以来已经一段时间了”。后边用一般过去时

如：
it is three years since he died.(自)他去世以来已经三年了。

而你的A属于另外一种
即： since 引导的从句，主句用现在完成时，从句用一般过去时！从句就是since后边的句子。
如：
He has studied very hard since he came to our school.
自从他来到我们学校，他学习就非常努力。

注意这个和：He has been a teacher since 1999. 仔细观察哦，这个是简单句

希望帮到你

Answer 3

现在完成时的基本结构。 four years has passed since Mike came to Tibet或 Mike has been in Tibet for four years

Answer 4

这是固定句式，It's XX years since +一般过去式

Answer 5

通常since后面加表示过去的时间点的句子。