He presented a masterpiece at the conference, …

Step 1: Analyze the question The sentence ends with a comma and a gap, so we need a question tag (a short question added to the end of a statement to confirm it).

Step 2: The concept Question tag rules:

1. Use the same auxiliary/verb tense as the main sentence.
2. If the statement is positive, the tag is negative. If the statement is negative, the tag is positive.
3. If the main verb has no auxiliary (simple past or simple present), use did/do/does in the tag.
4. The tag uses a pronoun that matches the subject.

Step 3: Solve

• Statement: "He presented a masterpiece at the conference"
• Subject: He → pronoun in tag: he
• Tense: simple past ("presented") → no auxiliary, so we use did
• Statement is positive → tag must be negative → didn't

So the tag is: didn't he?

Step 4: Check the options

• A. was he? – wrong auxiliary (was) and wrong polarity (a positive tag for a positive statement)
• B. wasn't he? – the polarity is right, but "was" doesn't match the simple past verb "presented"
• C. did he? – right auxiliary, but a positive tag after a positive statement is wrong
• D. didn't he? – right auxiliary (did), right polarity (negative), right pronoun (he) ✔

Answer: D. didn't he?

Exam tip: For question tags, ask yourself three quick things: (1) What is the tense or auxiliary? (2) Is the statement positive or negative, so I flip it? (3) Which pronoun replaces the subject? When there is no auxiliary in the past tense, always bring in did/didn't.