Correct option is C
The correct option to substitute the highlighted segment "Many a things are" is "a thing is."
· "Many a": This phrase is always followed by a singular noun and takes a singular verb. It is used to emphasize the number of occurrences or instances of something.
· Singular noun and verb agreement: After "many a," a singular noun and a singular verb should follow. Therefore, "thing" should be singular and the verb "is" should be used.
· Correct sentence: Many a thing is used for the show.
· Example:
Incorrect: Many a books are on the shelf.
Correct: Many a book is on the shelf.