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

in parentheses in the following sentence:
Feathers, fur, and animal skins are collected and studied (so that
positive identification of animal remains can be made).
a. adjective clause
b. adverb clause
c. noun clause

b. adverb clause

The function of the clause in parentheses is to provide a reason for why feathers, fur, and animal skins are collected and studied. Therefore, the correct answer is b. adverb clause.