Read the sentence. They had just started to cook dinner when their friends arrived at the door with some delicious take-out food. Which word is the adverb modifying a verb?
The adverb in this sentence is the word "at". The word "at" is also a preposition and this kind of preposition that also functions as an adverb is called a prepositional adverb. "At" here is an adverb of place and the verb it modifies is the word "arrived".