When she arrived at the concert hall, the singer walked through a crowd of cheering fans.

Which word is a preposition?

expressing a relation to another word or element in traditional grammar said to consist of a subject and predicate

When she arrived at the concert hall, the singer walked through a crowd of cheering fans.

Explanation:

A preposition is a word that shows the relationship between a noun and another word in the sentence.

The preposistion tells us that the singer's walking is going through the crowd.