Answer:
The correct answer is: a gerund.
Explanation:
A gerund represents a verbal noun which functions as a noun in a sentence. It always contains the termination "-ing". Also, it can act as a subject of the sentence, the object of a preposition, or the object of a verb.
e.g. Reading is good for your mind. I really enjoy reading.
In this case, a verbal "-ing" form functions as the noun in a form of a gerund.
