What is the range of the function represented by these ordered pairs?

(2,5), (3,5), (4,7), (10,7)

a) { 5, 7 }
b) { 2, 3, 4, 10 }
c) { 2, 3, 4, 5, 7, 10 }
d) { 5, 7, 10 }