(1) L passes through (5, 0) and K passes through (-5, 0) does not give any info about the slopes of the two lines; NOT sufficient.
(2) Lines L and K intersect to each other in the 2nd quadrant does not imply anything about the slopes of the two lines; NOT sufficient.
Combining (1) and (2), we get the following figure:

By looking at the above figure, we can easily say that line K has a positive slope and line L has a negative slope, so slope of line K is greater than that of line L; SUFFICIENT.
The correct answer is C.













