It is A. The problem asks for the interval when the marlin's height is always increasing. Therefore, you want to look at the left half of the parabola, as the line is going into the peak. The right half is declining. The peak is at around 2 (on the x-axis), so you know that the ending interval number has to be 2. The marlin's height begins to go up starting at 0, so the interval is 0 <= x <= 2. Any number past two is a declining height, and the increase starts at 0.
