20.When the hydrogen supply in the core begins to run out, and the star is no longer generating heat by nuclear fusion, the core becomes unstable and contracts. The outer shellof the star, which is still mostly hydrogen, starts to expand. At this phase the star is called a . a. White dwarf
b. Red dwarf
c. Red Giant
d. Black hole

that's what i got you can count the number of atoms

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.