What are the mathematical units, such as m, m, CM, cm? What do these things represent from small to large?
Length unit: km-km; Meter-meter, decimeter-decimeter; cm-cm；
Mass unit: ton-ton; kg-kg； G-g;
Area unit: square meters-meters? ; Square decimeter -DM? ; Square centimeter.-centimeter? ;
.......... (all in descending order)