Answer:
A, C, D are all functions
Explanation:
functions have a single output value for any unique input.
A can be rearranged to y = -2x - 8 which is linear with a non-infinite slope and is a function
C is a parabolic opening downward. Only a single output for each unique input.
D acts as a function as each unique input has a single output, even though that output may not be unique. The thing about table functions is it's hard to predict when a single input might create multiple output values.
B is not a function as an x input, lets say x = 2 will have outputs of y = 3 and y = -3.