Economic development results in low agricultural density because farmers require minimal land to feed the population.
people are able to leave agriculture for different fields.
fewer farms are needed to feed the population.
more people depend on factory-made food.
farmers lack workers to support their farms.

Answerepicenter;

Not sure just need the points

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.