What represents the third dimension in a topographic map and shows elevation?

The contour lines are the third dimension, showing the elevation of an area

Explanation:

Topographic maps are those that shows the topography of a particular area, type of relief and the location of hills and plains. They are provided with the north direction and the index that helps in a better understanding of the maps. They are commonly used by geologists and geographers.

The third dimension of the map i.e the height of the surface features is shown in terms of contour lines. Contour lines are the lines of equal elevations. They are shown by a number that depicts the height at that point from the mean sea level. The high mountains, valleys, and basins are easily identified from these maps.

volleyball players can not touch the net while the ball is in play

the answer is b, have negligible mass