Answer: C) Gerund phrase.
Explanation: A gerund is a noun formed from a verb which refers to an action, process, or state. In English it is formed by adding the particle "-ing" at the end of the root of a verb. In the given sentence we can see an example of a gerund phrase (formed by a gerund plus an object), which as we can see functions as a noun (notice that it can be replaced by the pronoun "it"). So the correct answer is option C.
