True or False: Slope and drainage are always calculated parallel to contour lines.

Answer: B — False

The correct assertion is that slope and drainage are not always calculated parallel to contour lines. In topographic mapping, contour lines represent points of equal elevation, and the slope is determined by the steepness or degree of incline between these lines. While contour lines can provide guidance for understanding the terrain's slope direction, water drainage does not always follow these lines directly, especially in areas with varying topography, manmade structures, or differing vegetation types that can affect flow patterns. In various situations, particularly in more complex landscapes or where human modifications exist, drainage can follow pathways that cut across contour lines, often directed by gravitational pull and natural pathways formed by geological features. Thus, stating that slope and drainage calculations are always parallel to contour lines does not account for these complexities, making the statement false.