. . . . . . . work hard, you won’t succeed.

Unless you don't
Unless you
Unless you do not
Lest you

The correct answer is: Unless you work hard, you won’t succeed.

The word “unless” means “if not.” In this sentence, it is used to introduce a condition that must be met in order for the result to occur. In other words, if you do not work hard, you will not succeed.

The other options are incorrect because they do not convey the same meaning. The word “if” could be used in place of “unless,” but it would not be as strong. The word “but” would introduce a contrast, which is not what is intended in this sentence. The word “lest” is an archaic word that is not commonly used in modern English.

In conclusion, the correct answer is: Unless you work hard, you won’t succeed.