At first ,we should know that :
The relation between x and y will be a function when each value of x appeared one time
We will check the options:
A. for the figure of option A, each value of x connected one time to a value of y
B . there are 2 arrows from 0 and 1
C. the values of x = -1 , connected four times to the value of y
So, the answer is option A
