Select the letter of the term that identifies the function of the clause

in parentheses in the following sentence:
The United States Fish and Wildlife Service operates a forensics
laboratory that helps officials find evidence to use against (whoever
kills or captures endangered animals).
a. adjective clause
b. adverb clause
c. noun clause

c. noun clause

The letter that identifies the function of the clause in parentheses in the given sentence is c. noun clause.