Answer:C
Step-by-step explanation:
For every function; f(x) = y
Each value of 'x' produces only one output 'y'
A,B and D are not functions because this rule is violated. It is observed that on the graphs of A,B and D, there exists a value of x that produces two outputs(y).
Hence, C is the correct option as it produces only one output 'y' for each value of x.
