Topic: Gerunds & Participles,

Best Answer Explained in Below-:

In the sentence "The child saw a flying bird," the underlined word "flying" serves as an adjective that describes the noun "bird." To classify "flying," we must understand the different forms of verbs and how they function in this context.

1. **Participle**: A participle is a verb form that can function as an adjective. In this case, "flying" is the present participle of the verb "fly." It describes the bird and tells us more about it—specifically, that it is in motion.

2. **Gerund**: A gerund, unlike a participle, functions as a noun. For example, "flying" could be a gerund in a sentence like "Flying is fun," where it serves as a subject. However, in our original sentence, "flying" does not act as a noun.

3. **Infinitive**: An infinitive is the base form of a verb, usually preceded by "to" (e.g., "to fly").

4. **Finite**: A finite verb shows tense and agrees with the subject. "Saw" is finite in this sentence, while "flying" is not.

Thus, "flying" is best categorized as a participle, as it modifies "bird" and reflects an ongoing action related to the noun. Hence, the correct answer is A) participle.