Which can be used as the subject of a sentence? a gerund. a participle. an adjective. an adverb

The answer to your question would be that the one that can be used as the subject of a sentence is the following one: Gerund.

a) Driving can be very dangerous

A gerund is a word based on a verb that functions as a noun in the sentence. Therefore, they can be the subject of the sentence, the direct object, or the inderect object. They always end in -ing.  In A, "driving" is a gerund which is acting as the subject of the sentence.

i'm not good at running

a.) literature that explores grotesque characters and eerie, violent occurrences in a dreary setting.