Choose the correct question tag?

The correct answer is Option (1) → He said that, didn't he?

Question tags:

• A positive statement takes a negative tag, and a negative statement takes a positive tag.
• The tag uses the helping verb of the statement; when there is none, "do / does / did" is used in the same tense.
• The tag ends with the pronoun for the subject.
• This sentence: "He said that" is positive and in the simple past with no helping verb, so the tag is "didn't he?"
  Example: She sang well, didn't she?

Why the Other Options are Incorrect?

Option 2: He said that, did he? — Incorrect. A positive statement needs a negative tag; "did he?" is positive.

Option 3: She didn't do that, didn't she? — Incorrect. The statement is negative, so the tag must be positive.
Corrected: She didn't do that, did she?

Option 4: They will come, will they? — Incorrect. The positive statement needs a negative tag.
Corrected: They will come, won't they?