Answer:
b, c, e
Step-by-step explanation:
A function has unique x-values (inputs). Several of the relations here are functions:
a. {(0,1), (0,2), (0,3)} . . . repeated x-value of 0, not a function
b. {(1,1), (2,2), (3,3)} ... function
c. {(1,1),(2,1),(3,1)} ... function
d. {(1,1),(2,2),(2,-2)} . . . repeated x-value of 2, not a function
e. {(1,-1),(2,-2).(3,-3)} ... function