The heat of fusion for water is the amount of energy that must be absorbed for water to a. evaporate b. freeze a. boil d. melt

The answer would be A. Evaporation. Heat of fusion in any types of matter is the amount of heat transfer to a matter that allows it to change its form by gathering or absorbing an amount of heat that could change is form either its from solid to liquid, liquid to gas or vice versa. 

Hydrogen is the most abundant element on the periodic table..hope it .