1.I will wait for Tim ___ he gets back.(答案是as,为什么till不行)

1.I will wait for Tim ___ he gets back.(答案是as,为什么till不行)
A.that B.as
C.till D.when
2.Although it was so cold ,___ he went out without an overcoat.
（答案是C,为毛啊）
A.but B.so
C.yet D.and
3.He's already back to Australia,____?（答案是A,为什么不是he has already ）
A.isn't he B hasn't he
回答的精彩额外追加分，反正咱分多 = =