Explanation:

- "If he doesn't reach the station in time, he would sure miss the train." The sentence uses "would sure," which is incorrect for expected outcomes.

- Option 1: would surely miss - Not applicable. "Would" is used for hypothetical situations, which doesn’t match the conditional "if he doesn't."

- Option 2: No substitution - Not applicable because the current phrase is incorrect.

- Option 3: will sure missing - Incorrect construction.

- Option 4: will surely miss - Correct use of "will" for likely future outcomes and "surely" for emphasis, making it suitable for the sentence.