Parts of speech. choose the correct answer. words such as slowly, very, and tomorrow that answer the questions how? and when? are (a) adverbs, (b) adjectives, (c) nouns, (d) conjunctions:

(a) adverbs,

Explanation:

Words like slowly, very, quickly, fastly and tomorrow that gives the answer to the questions How? are Adverbs. An adverb is a word tells more about a verb, and most of the time answers the questions how often? how? when? what way? where?  

Usually, there are five kinds of the adverb, and when the word indicates that how something is done as the question is being asked here, it is called Adverbs of Manner.

answer; ///i believe the best answer from the above question is (c) a method of making a purchase by trading items instead of using money; plz check first.good luck