--- Is Tom still smoking?
--- No. By next Saturday he for a whole month without smoking a single cigarette.
A. will be
B. will have gone
C. will have been
D. has been going
网友回答
A. will be
B. will have gone
C. will have been
D. has been going
解析：“by+将来某一时间”常与将来完成时态连用。