Read the sentence.
tell whomever you meet about this new opportunity.
the bolded words are what kind of clause?
a) adjective clause
b) adverb clause
c) noun clause

The bolded words are noun clause.

A noun clause is a dependent clause that acts as a noun. Noun clauses begin with words such as how, that, what, whatever, when, where, whether, which, whichever, who, whoever, whom, whomever, and why. Noun clauses can act as subjects, direct objects, indirect objects, predicate nominatives, or objects of a preposition.

The correct answer between all the choices given is the third choice or letter C. I am hoping that this answer has satisfied your query and it will be able to help you in your endeavor, and if you would like, feel free to ask another question.