Read the sentence. our field, engineering, has made great advances in fire safety. how does the gerund function in the sentence? a. as a subject b. as an appositive c. as a direct object d. as an indirect object

The correct option is B.
The gerund in the given sentence is engineering. A gerund refers to words which are formed with verbs but which act as nouns in sentences. Gerunds usually end with 'ing'. In English language, an appositive refers to a noun or a noun phrase that is used to rename another noun that is located beside it. In the sentence given above, the word 'engineering [which is a gerund] functions as an appositive.