Answer:
X represents nitrogen base pairs- adenine, thymine, guanine, and cytosine.
Explanation:
DNA molecule is a molecule that carries genetic information for growth, functioning, development, and reproduction. It is composed of nucleotides that contain a phosphate group, a sugar group, and nitrogen bases (adenine, guanine, thymine, and cytosine).
Nucleotides are linked together to form two long strands that coiled spirally to create a structure called a double helix. Just think of the double helix as a ladder. The phosphate and sugar groups would be the two sides of the ladder, while the nitrogen bases would be the rungs of the ladder. The bases adenine pairs with thymine, while guanine pairs with cytosine.
Thus, the correct answer would be base pairs.