The molecules of living matter that provide building blocks are mostly based on:

A. Carbon

The molecules of living matter that provide building blocks are mostly based on carbon. Carbon is unique among the elements in its ability to form a wide range of complex compounds, including the large, complex molecules that make up the structural components of living organisms. These molecules, called organic molecules, include sugars, amino acids, nucleotides, and fatty acids, among others. Carbon-based molecules can bond with each other in various ways to form even larger, more complex structures such as proteins, carbohydrates, and DNA.

B. Nitrogen is an important component of many organic molecules, including amino acids, nucleotides, and DNA.

C. Hydrogen is a component of many organic molecules, including sugars, amino acids, and fatty acids.

D. Ammonia is not a major building block of living matter. It is a nitrogen-containing compound that is toxic to most living organisms in high concentrations.