Answer:
A, B, and C.
Explanation:
We have the equation:

Let’s distribute the left. This yields:

Let’s add 12 to both sides:

And subtract 4x from both sides:

We get the true statement 0=0.
Hence, A is correct.
Because it is a true statement, any input will yield an equivalent output.
Hence, B is also correct.
We also have the form a=a, where a is 0.
Hence, C is also correct.
Therefore, our correct answers are A, B, and C.