The formula k2s indicates that:

a. the potassium ion is twice the size of the sulfur ion
b. sulfur and potassium form a double covalent bond
c. there are two potassium ions for each ion of sulfur
d. there are two sulfur ions for each potassium ion

1. they vary with a higher number because boiling is way hotter than melting

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.