Correct statement among the following is

a) All macromolecules are not necessarily organic polymers. While organic polymers are macromolecules, there are also macromolecules that are not organic polymers, such as some forms of inorganic polymers.

b) The physical and mechanical properties of a polymer are different from those of its monomer. A polymer is made up of many monomers linked together by covalent bonds, resulting in a larger and more complex structure. Therefore, the properties of the polymer are different from those of the individual monomers.

c) Majority of the bonds in a polymer molecule are covalent bonds. Covalent bonds are formed by sharing of electrons between atoms, and they are the strongest type of chemical bond. Polymers are formed by the repeated bonding of monomers through covalent bonds, resulting in a long chain of molecules.

d) Vitamins are not polymers. Vitamins are organic compounds that are essential for normal physiological functions, but they are not polymers.