Answer:
The correct answer is: gerund.
Step-by-step explanation:
In the English language, the gerund is a non-finite verb form, also known as the “-ing form”.
The gerund is composed of verbs, but it always acts as a noun and it can appear as a subject or object of a verb.
We use gerund to form any continuous tense, by using an adequate form of the verb "to be" and the -ing (gerund) form.