Which mountain chain runs from mexico north through the united states and canada, along the western side of the region?

a.) appalachian mountains

b.) pacific rim mountains

c.) sierra nevada mountains

d.) rocky mountains

Answerleveling;

Convection current is the main process through which heat is transferred in bulk from one location to another through the cyclic motion of a large volume of substance.

The highest point of a hill (or mountain) is a single point.
a single point can only be precisely marked with a dot. 
putting on a contour line is impossible  on a single point because the contour line is created after multiple points that have the same hight are marked, and after that, all of those points are connected with a line that creates a closed area. so the highest point, as said above, is a single point, there are no other points with the same height, so the only possible way for it to be marked is with a dot, and there is no possibility for a contour line.