If a man is to succeed,he must work as hard as he can.
答案：B
is to succeed ：已经决定并且去做
If a man is to succeed,＝＝if a man wants to succeed,
翻译：一个人想要成功,就必须尽量努力工作.
A ：will 主将从现,所以wii不能放在（主将从现）从句里,不能说：if a man will succeed,- - --.
C:一般强调计划打算,并非一定会去实施.
D:语气太弱,并含有虚拟的味道,所以不行.