What is the structure that contains the genetic material of all organisms?

The correct choice is DNA, as it is the primary molecule that contains the genetic instructions necessary for the development, functioning, growth, and reproduction of all known living organisms. DNA, or deoxyribonucleic acid, is organized into structures called chromosomes, which package and protect the genetic material within the nucleus of eukaryotic cells. Each DNA molecule consists of a double helix formed by nucleotide subunits, which vary in sequence to encode the vast diversity of genetic information.

While RNA, or ribonucleic acid, plays a crucial role in various biological processes, such as protein synthesis, it typically serves as a messenger carrying instructions from DNA. Proteins, on the other hand, are synthesized based on the genetic code provided by DNA, but they do not contain the genetic material themselves. Chromosomes are structures made of DNA and proteins; they serve to organize and condense the genetic material during cell division but do not encompass the entirety of the genetic instructions. Therefore, DNA is the molecule that holds the genetic code essential for all life forms.