Hydrogen and hydrogen+fluorine.
Carbon - it is the basis for organic chemistry.
sodium and flourine
Arsenic.
calcium and lithium are both metals and dont form bond with each other. sodium and flourine form ionic compound, sodium fluoride. nitrogen and oxygen form covalent bond in the nitrogen oxides. helium and argon are both nonmetals / noble gases and dont form bond with each other.
Most likely, that would be James Bond.
hydrogen sulfide
A covalent bond is most likely to be polar when there is a large difference in the electronegativity of the two atoms that form the bond.
It would form a ionic bond due the the Mg2+ and 2Cl-.
Oxygen
With itself or with 5A group
Li, or lithium, is the element most likely to lose electrons in a chemical bond. Lithium has 1 valence electron.
If everything else is the same, the AAA would have a higher price (more expensive) while the BBB would most likely have a higher yield (higher return)