Topic: Adverb (ক্রিয়াবিশেষণ),

Best Answer Explained in Below-:

In the sentence "The flight is leaving shortly," the word "shortly" serves as an adverbial. Adverbials are words or phrases that modify verbs, adjectives, or other adverbs, providing additional information about the action or state conveyed in the sentence. In this case, "shortly" specifies the time frame of the verb "is leaving," indicating that the flight is departing in the near future.

Unlike a complement, which typically completes the meaning of a verb or noun, or an object, which directly receives the action of a transitive verb, "shortly" does not fulfill such roles. It does not complete the meaning of the verb nor does it receive an action, but rather enhances it by providing temporal context. Additionally, it cannot be a subject since a subject is typically a noun or noun phrase that performs the action of the verb.

Thus, the correct classification of "shortly" in this context is as an adverbial, as it modifies the action of leaving by indicating when the action will take place.