As per the rule, oxidation number of alkaline earth metals in their compounds is +2. Oxidation number of oxygen in it's compounds is -2(except peroxides) and the sum of oxidation numbers of all the elements of a neutral compound is zero.
The amount of energy in molecules of matter determines the state of matter. Matter can exist in one of several different states, including a gas, liquid, or solid state. ... A gas is a state of matter in which atoms or molecules have enough energy to move freely.
Cylinder D
temperature is the measurement of average kinetic energy of a sunstance. since cylinder D has the highest average velocity, it has the highest average kinetic energy among the 4 cylinders, thus cylinder D is the hottest.