What changes when moving downwards from fluorine to chlorine on the periodic table

c is the answer because when something is left after something evaporates that shows the chemical change.

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation:

answerspecific gravity;