What part of speech is word tearfully Tearfullu,I hung up the phone

Since "tearfully" is used in this sentence to modify the action of the verb "hang-up," it is an adverb.

Hint - with a few notable exceptions, most words ending in "ly" are adverbs, as they are usually used to modify either verbs (as above) or adjectives.

Now - why did you post this question in a Business Management forum?