An adverbial is a word (an adverb), phrase, or clause which modifies (changes, restricts or adds to the meaning of) a verb. An adverbial can be a noun phrase (we met that afternoon), a prepositional phrase (we met in the cafe), or a clause (we met because we needed to talk) as well as an adverb, but always functions to modify the meaning of a verb. A sentence can contain just one adverbial or several. The wrong alternative is the letter: