12.i’ll give the message to her as soon as she_________.

12.i’ll give the message to her as soon as she_________.
A.return B.will return C.returns D.returned
13.great changes_________in shanghai in the past twenty years.
A.has taken place B.have taken place C.had taken place D.took place
14.i wonder if chris_______to see me tomorrow.If she__________i will take her to the garden.
A.will come…will come B.comes…comes
C.will come…comes D.comes…will come
15.the story_______to one of my friends three years ago.
A.was happened B.is happened C.happened D.happening
18.by the end of the coming2003,the foreigners here________all parts of china.
A.have visited B.will have visited C.will visit D.will visit
21.the famous singer________here if he comes here.
A.will welcome B.will be welcome C.is welcome D.welcome
请从语法的角度详解.