Answer:
I have/had seen a duck.
Explanation:
The sentence "I seen a duck" is ungrammatical because the verb "seen" is in participle form and It requires the auxiliary verb "have" to show tense.
The correct versions would be:
- I have seen a duck. (in present perfect tense)
- I had seen a duck. (in past perfect tense)
We can also say this sentence in a correct form changing the tense of the verb:
- I saw a duck. (in past tense)
- I see a duck. (in present tense)
