How can the sentence 'You won't succeed unless you try harder' be rewritten using 'until'?

The sentence "You won't succeed unless you try harder" emphasizes a condition that must be met in order to achieve success, specifically the need to put in more effort. When rewritten using "until," the transformation retains this conditional meaning by stating that success will not occur up to the point where the effort is applied.

The correct choice states, "You won't succeed until you try harder," which clearly conveys that success is contingent upon the effort being made. The use of "until" appropriately indicates that the lack of success persists until the action of trying harder is taken. Thus, the sentence maintains the original's intention while using the new phrase.

In contrast, other choices either do not capture the original meaning accurately or alter the condition too significantly. For example, one option implies that success can occur without the need to try harder, which changes the core message of the original sentence.