What is the part of speech of the underlined word in the sentence? there was no electrical power throughout the city after the storm. the underlined word is throughout a. adjective b. adverb c. preposition d. conjunction

The word throughout is used as a C. preposition in this sentence.

When you are referring the the physical location, such as here (throughout the city), then it is a preposition.

If it is not physical, such as in - throughout her entire life - then it is an adverb.