C)
Metallic solids consist of metal ions which are surrounded by delocalized electrons.
Such ions are said to be isoelectronic
The chemical symbol that represents the element silver is B. Ag
D) Helium (He) is the second most abundant element in the universe, the first one being hydrogen, and helium is followed by: oxygen, carbon, neon, iron, nitrogen, silicon, magnesium, and sulfur.
