The preposition is defined as the word that has be placed prior to a noun or pronoun in making a sentence with phrase. This phrase is going to modify another word in the given sentence.
In the above given sentence, “during” is word that is placed prior to pronoun “storm”. The word “lost” is verb. Power is prepositional phrase.
Thus, the options (d), (c) and (a) are incorrect.
In the above given sentence, “during” is word that is placed prior to pronoun “storm”. The word “lost” is verb. Power is prepositional phrase.
Therefore, the correct option is – b. during.