You have to work hard if you want to succeed . . . . . . . . life. A. in B. from C. for D. to

The other options are incorrect because they do not indicate a goal or destination.

• The preposition “in” is used to indicate a location or position. In this case, it would not make sense to say that you have to work hard “in” life.
• The preposition “from” is used to indicate a starting point or origin. In this case, it would not make sense to say that you have to work hard “from” life.
• The preposition “for” is used to indicate a purpose or reason. In this case, it would not make sense to say that you have to work hard “for” life.