Which Set of Ordered Pairs Represents a Function from P

Multiple Choice

Which set of ordered pairs represents a function from P to Q? P = {5, 10, 15, 20} Q = {-2, 0, 2}

A) {(5, -2) , (10, 0) , (10, 2) , (15, 0) , (20, -2) }
B) {(15, -2) , (15, 0) , (15, 2) }
C) {(15, 0) , (10, -2) , (5, 0) , (10, 2) , (15, -2) }
D) {(10, 0) , (15, 2) , (20, 0) }
E) {(5, 2) , (15, 0) , (5, -2) , (15, 2) }