Choose the Adjective from the given sentence:
The whole class is listening to the teacher carefully.

An adjective is a word that qualifies a noun or a pronoun. 
Example: I have a pink pencil. 
The word 'whole' is qualifying the word 'class' which is a noun. 
Therefore it is an adjective. 
'Whole' is also used as a noun. 
It means 'all of something'. 
Example: She had to choose the best as she could not accept the whole.