Question

Read the sentence.

Answer 1

C.  adjective clause

As you may know, a noun is a person, place, or thing.  An adverb describes a verb.  And, an adjective describes a noun.  When nouns, adverbs, and adjectives are more than just one word, they are called clauses.  The bolded words “whom Mr. Stein chose” are actually describing the noun “student.”  And, because we know that words describing nouns are adjectives or adjective clauses, it is understood that “whom Mr. Stein chose” is an adjective clause.

Answer 2

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.