Which Set of Ordered Pairs Represents a Function from a to B

Multiple Choice

Which set of ordered pairs represents a function from A to B
A = {a,b,c} and B = {4,3,1,2}

A) {(a,4) , (b,3) }
B) {(a,2) , (c,3) , (b,4 ) }
C) {(a,4) , (c,1) }
D) {(a,1) , (c,3) , (c,1) , (b,4) }
E) {(a,4) , (c,3) , (c,1) , (b,1) }