Refer to the Following Graphs to Determine an Appropriate Response $y = [ [ x ] ]$

Multiple Choice

Refer to the following graphs to determine an appropriate response.
-Which is not the graph of a function? What is its equation?

A) graph D; $y = [ [ x ] ]$
B) graph $A ; y = x$
C) graph $B ; x = y ^ { 2 }$
D) graph $C ; y = \sqrt { x }$