What is the gerund in this sentence as they were waiting for the bell to ring, the chattering students were complaining about the new regulation for wearing hats at school.

The gerund in the sentence provided is "wearing".

Explanation: A gerund is a non-finite verb form that ends in -ing and acts as a noun. Moreover, a gerund can act as the subject, the direct object, the subject complement or the object of a preposition in a sentence. In the sentence provided, "wearing" is the only gerund as "wearing" is acting as a noun and functioning as the object of the preposition "for". In contrast, "waiting", "chattering" and "complaining" are present participles.

hey! what was the rest of the question?