Pretend the y-axis is a wall, on the left side it is decreasing and on the right it is increasing, so A. and B. aren't correct. C. and D. are left, x<0 means on the left side of the y-axis because x (any number) is less than 0 and on the left side it is decreasing so C. isn't correct so D. is your answer because x>0 means x is greater than 0 so it's on the left side of the y-axis.
