This molecule is CH4, methane.
a. It has 4 simple covalent bonds. These atoms, C and H, are nonmetals and tend to form covalent bonds.
Each union between H and C is a bond.
b. These bonds are formed because the C atom has 4 electrons on its last shell and shares its electrons with the electrons of the 4 H that share their electrons too.
After sharing electrons, C gets 8 electrons on its last shell, so it gets the Octet and the 4 H get the doublet. Thus, this molecule gets stabilized.
These atoms share electrons.