Question

—— Is Tom still smoking ?
—— No.By next Saturday he ＿＿＿＿＿＿＿ for a whole month without smoking a single cigarette

1. A.
   will go
2. B.
   will have gone
3. C.
   will have been
4. D.
   has been going

Answer 1

B
by 后跟将来的时间状语时，主句要用将来完成时。go without 意为“在缺……的情况下对付”。