How do Hydrogen-1, Hydrogen-2, and Hydrogen-3 differ from each other?

your answer would be a. 12.5 kg

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: