Determine whether or not each relation is a function.
a. {(1,4), (1,5), (2,3)}
b. {(A,C),(C,E),(A,B)}
c. {(1, 1), (2, 2), (3,3)}
d. {(-3,-2), (-2,-1),(-1,0)}
e. {(B,C),(D,C),(E,C)}​