All the above is correct.
Answer.
The answers is A; The physical and chemical properties of HCl are different from those of H2 and Cl2.
Explanation;
Hydrogen chloride is a gas, which is a molecule made up of a hydrogen and a chlorine atom bonded by a single bond.
The chemical and physical properties of HCl differs from those of hydrogen and chlorine. For example; they have different molecular weight; HCl is colorless, while chlorine is greenish yellow and hydrogen is colorless
Complex molecules are made up of other elements bonded with carbon. Carbon is able to bond with other molecules so easily because it has four valence electrons.
