Direct current is produced by batteries, fuel cells, rectifiers, and generators with commutators
The answer for the above question is the unsaturated fats. Fats play a vital role in the body such as giving energy and also helping the body absorb vitamins. Dietary fats also play a major role in regulation of cholesterol levels in the body. Dietary fats consists of the saturated fats, trans fats, monounsaturated and poly unsaturated fats.
I think the correct answer would be mass of the shells. According to the law of conservation of mass, mass can never be created not destroyed. Therefore, mass here should be constant before the transformation and after the process. Hope this helps.