When tap water contains high levels of calcium, a substance called calcium carbonate (CaCO3) can build up at the mouths of water faucets. This buildup, called limescale, can prevent water from flowing through a faucet properly. To remove the calcium carbonate, you can scrub the faucet with citric acid (C6H8O7). Citric acid combines with calcium carbonate to form calcium citrate (Ca3C12H10O14), carbon dioxide gas (CO2), and water (H2O). The calcium citrate washes away easily, allowing water to flow through the faucet again. Which are products?

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.

i think is conclusions.i think so

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.