Bunuel wrote:

Does point (10,10) lie on line m?

(1) Line m passes through point (10,11).

(2) Line m passes through point (11,10).

the answer should be C

1. we don't know the slope. If we have an undefined slope, then we have a vertical line, and the point 10,10 is on the line. but if the slope is anything but 0, it is not...not sufficient.

2. same thing - If the slope is 0, then we have a horizontal line, and the point is on the line m, if not, then not...

1+2

we have 2 points on the line m - we can find the slope. point 10, 10 is not on the line

sufficient.