Answer:
only B
Explanation:
to be a function each value of x must have exactly one value of associated y.
in A x = 1 has 2 different y values (1 and 3) associated. no function.
in C the curve shows that many values of x have multiple different y values.
e.g. x = 0 has y = -2, 0 and 2
no function.
in D x = 6 has 2 different y values (5 and 7). no function.