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

in parentheses in the following sentence:
Wildlife forensic science is an entirely new field, which is being
staffed by trained wildlife experts as well as by those (who have
experience in police crime labs).
a. adjective clause
b. adverb clause
c. noun clause

a. adjective clause

The function of the clause in parentheses in the sentence is an adjective clause.