Explanation:

- The sentence starts with "He is diligent; therefore," implying a cause-and-effect relationship.

- The word "therefore" indicates a positive outcome as a result of being diligent.

Option 1: he will not succeed

- This option contradicts the positive connotation of "diligent" and "therefore."

Option 2: he can't succeed

- Similar to option 1, it doesn’t logically follow the positive implication.

Option 3: he will succeed

- This is the correct completion as it aligns with the expectation that diligence leads to success.

Option 4: he succeed

- Grammatically incorrect; it should be "he succeeds" or "he will succeed."

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