The correct option is A Singing -gerund
A gerund is a verb form which acts as a noun.A present participle form is the form of a verb, ending in-ing in English, which is used in forming continuous tenses. Option A) singing- gerund is correct as the word acts as a noun. The other options are wrong as singing is not used as a continuous form of verb and is is the auxiliary verb here. The correct answer is A) singing- gerund.