Topic: Adverb (ক্রিয়াবিশেষণ),

Best Answer Explained in Below-:

In the sentence "I 'usually' get up early," the word "usually" acts as an adverb. Adverbs are words that modify verbs, adjectives, or other adverbs, providing more information about how, when, where, or to what extent an action occurs.

In this case, "usually" modifies the verb "get up," indicating the frequency with which the speaker engages in this action. It tells us that getting up early is a common or typical occurrence for the speaker, rather than something done occasionally or infrequently. This frequency aspect is a key characteristic of adverbs, further emphasizing that "usually" fits this role.

While "early" in the sentence also functions as an adverb—modifying "get up" by describing the time at which the action takes place—"usually" specifically addresses the regularity of the action. Therefore, among the provided options, "D: adverb" is correct for "usually," as it conveys essential details about the action's frequency. This distinction between the two adverbs differentiates their roles in the sentence while affirming the grammatical structure.