M is the slope of the first straight line and the y-axis intercept of the second straight line.

N is the y-axis intercept of the first straight line and the slope of the second straight line.

If m>0, then the intersection of another straight line and y is on the semi-axis of y axis.

If m

The same is true for n.

So A is wrong (slope is positive, intercept is positive and negative) and B is wrong (slope is positive and negative, y-axis intercept is positive).

C is correct, but D is definitely not.