Question

It is/has been +since 用法。请认真看我的问题。请求大师解答。菜鸟靠边？

1，It is three years since he began to smoke.2，It is three years since he has smoked. 两句均意为：他吸烟已有3年了。可以理解 还有这句3，it is three years since he smoked 他已经不抽烟三年了。也勉强可以理解。但是我不能
理解第二句，第二句意思完全和第三句一样啊？我翻了牛津字典看我发的图片。it is twenty years since I have seen her 意思是我已经二十年没见她了！所以到底since 后用过去时还是完成时。？意思一样吗？ 还有it is和it has been 加since有没有区别。我觉得网上说的it is three years since he has smoked 翻译是错的 还是应该翻译成他已经不抽烟三年了。不知道对不对。搞混了，请求大师解答！跪谢！

Answer 1

我认为第二句是错误的
因为since +从句 (从句时态要用一般过去时)
It's +一段时间 +since +从句 (过去时)
或
It has been +一段时间+since +从句(过去时)

It is three years since he began to smoke.

追答

It has been three years since he began to smoke.

Answer 2

since的三种不同用法