Not sure which one is correct..

Note that the function is at a max  at  x   =  2

From there....the function decreases as we move to the right...so...it decreases on    ( - 2, inf )  =   2 < x < inf ⇒ "C"

  {  Positive infinity is to the right....negative infinity is to the left.... on the x axis }

I think that you are getting confused..."interval"  usually refers to  the   x axis  values

The function decreases to -infinity along the y axis  as we move to the right

So  we can say that, as we move toward infinity on the x axis....the function decreases to -infinity along the y axis

Does that make sense....???