Question

he saw the rainbow. (interrogative sentence using 'did')

Answer 1

I think it should be- Did he saw the rainbow?

Answer 2

here is you answer
interrogative means sentences with question mark
so its interrogative will be :
DID HE SEE THE RAINBOW ?

explanation /: in this sentence we were directed to use ' did' so in interrogative helping verbs come first as 'did' os also replaced at first after that subject comes then always remember with 'did' we use 1st form of the verb as directed in this sentence. and then rest part will be followed at last 'question mark' is important in interrogative.




hope it helps you