Read the sentence.
the student whom mr. stein chose was first in her class.
the bolded words are what kind of clause?
adverb clause
adjective clause
noun clause

Since the bolded words aren't specified in the question.

"Mr. Stein chose was first in her class" represents a noun clause.
"whom" represents a adjective clause

A clause is a statement or segment of a sentence which has its own subject and immediate predicate or can stand on its own unlike phrases. For example, Maria was driving her car when she carelessly hit another car. The bold text indicates a clause.