Identify the preposition in the following sentence: before leaving for practice, make sure you have packed a lot of water; it's hot outside!
a. before
b. leaving
c. practice
d. packed

The word "before" is a preposition.

Explanation:

Before works as a preposition, an adverb and as a conjunction, it is a preposition of time and place, the other options are verb, am two nouns, packed is a past participle conjugation of pack, the other two options are nouns that refer to an object thing or situation in the sentence, option A is the only preposition.