A is one of two classes of molecules that are responsible for the storage, expression, and transmission of genetic information.

The correct answer is: DNA.

Explanation:

DNA or Deoxyribonucleic acid is the genetic material that is transmitted from the parents to the offspring.It encodes for  genes that gives rise to one of the most important structural and functional unit of cells, that is, the Proteins.The DNA is composed of a double helical backbone, made up of alternate deoxyribose sugar and phosphate groups linked by phosphodiester bonds. Each sugar molecule is linked to a nitrogenous base, purine or pyrimidines.The purines are Adenine(A) and Guanine(G) and the pyrimidines are Thymine(T) and Cytosine(C).Adenine of one strand of the helix forms two hydrogen bonds with the Thymine on the other strand and the Guanine of one strand of the helix forms three hydrogen bonds with Cytosine on the other strand.In some organisms, RNA or Ribonucleic Acid functions as the genetic material.