1.I suppose that when I come back in 2008 all these new bridges will__
A have built B have been built C be building D be built
2.BEN is always rude,__is why people tend to avoid him
A which B such C it D as
3.Did he start giving up smoking only yesterday?
No ,He began __he saw the news last month.
A the moment B because C if D till

1,B.
2008回来时，时将来的时间，到那时所有的建筑都将完工，所以用将来完成时态。
2,A.
which引导的是一个非限制性定语从句，指代前面的句子内容。
3,A.
the moment引导一个时间状语从句。意思是“一……就”。