We have been working together since 1970.对1970划线,该如何提问?
问题描述：
We have been working together since 1970.对1970划线,该如何提问?
答
since when have you been working together?
若since 1970划线，则是how long have you been working together?
答
since when have you been working together
答
Since which year have you been working together？
Since when have you been working together？
答
How long have you been working toghther?
有不会的可以再问我
答
How long have you been working together?