Answer:
a.) An adverb
Explanation:
An adverb is a part of speech that modifies or describes a verb in a sentence.
There are various kinds of adverbs such as: adverb of time, place, frequency, degree and so on.
You can identify an adverb in a sentence by checking to see if the word modifies the verb in the sentence.
In the sentence: "I know better" the adverb "better" describes the verb "know". Better as used in the sentence is a comparative form of the word well. The adverb describes how well the speaker knows whatever he is talking about.
