英语问题3!1.So far as I know,the library _________at weekends.(

英语问题3!
1.So far as I know,the library _________at weekends.( )
A.is not opened
B.does not open
C.will be opened
我觉得A,C也可以,为什么只能选B,为什么A,C不对呢?
2.Father is busy writing postcards this morning and _______ten so far.
A.has wrriten B.has been writting
为什么选B,为什么不能选A,A和B有什么区别?
3.The old man went to the information center soon after his arrival as the city_______so much.
A.had changed B. has changed
为什么选A,B怎么不行呢?