We usually head straight home after working hard with the horses.
which underlined adverb can also be used as a noun?
hard
home
straight
usually

The adverb that can also be used as a noun is "home".

Explanation: An adverb is a word that modifies a verb, an adjective or another adverb. Moreover, adverbs are generally found after the word they modify. On the other hand, a noun can make reference to a thing, a person, an animal, an emotion or a place. Furthermore, nouns are usually modified by adjectives. The word "home" can be used either as an adverb or as a noun since it can be used to modify a verb, an adjective or another adverb or it can be used to make reference to a place and to be modified by adjectives or  determiners.  

you have approval for this story

explanation:

and also the mystery girl it might be someone that she might know in her school