Help me please

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.

intermolecular forces are the forces between molecules or particles.

there are two kinds of van der waals forces: weak london dispersion forces and stronger dipole-dipole forces.

in molecule of water there are dipole-dipole forces between negatively charged oxygen from one molecule of water and positively charger hydrogen of another molecule of water.

hydrogen bond is an electrostatic attraction between two polar groups that occurs when a hydrogen atom (h), covalently bound to a highly electronegative atom such as flourine (f), oxygen (o) and nitrogen (n) atoms.  

∠gdh and ∠edh on edg.

answer is c