It would be D, fertilization.
A nitrogenous base, or nitrogen-containing base, is an organic molecule with a nitrogen atom that has the chemical properties of a base. The main biological function of a nitrogenous base is to bond nucleic acids together. A nitrogenous base owes its basic properties to the lone pair of electrons of a nitrogen atom.
neurons are specialized cells that generate and conduct electrical impulses throughout the body.
D, is the Answer hhfthvvvbh
