Explanation:

- The original sentence is, "He came late, wasn't it?"

- Option 1, "isn't it": This would be used after a present tense verb or a current situation, not a past event.

- Option 2, "didn't he": This is the correct option. After a statement in the past tense like "He came late," the proper tag is "didn't he" to affirm the past action.

- Option 3, "No improvement": This would apply if the sentence were correct as is, but it's not in this case.

- Option 4, "did he": This would actually be used for a negative statement, such as "He didn't come late, did he?"

So, the correct answer is:

Option 2: didn't he