What is the range of the function: {( 1 , 2 ) , ( 2 , 4 ) , ( 3 , 6 ) , ( 4 , 8 )}

A. ( 1 , 2 , 3 , 4 , 6 , 8 )
B. ( 1 , 2 , 3 , 4 )
C. ( 2 , 4 , 6 , 8 )
D. ( 6 , 8 )