If the Function Is One-To-One, Find Its Inverse

Multiple Choice

If the function is one-to-one, find its inverse. If not, write "not one-to-one."
-{(13, -6) , (-5, 5) , (6, -20) }

A) not one-to-one
B) {(13, 5) , (13, -5) , (-20, 6) }
C) {(-6, 13) , (5, -5) , (-20, 6) }
D) {(-6, 13) , (6, -5) , (-20, 5) }