PLSSS HELP IF YOU TURLY KNOW THISS

A. Exposition. It tells you the answer essentially in the description of the word by saying that it lays out the plot for the book and introduces the conflict.

Okay, biology isn't exactly my strongest subject (it never has been), but i'm pretty sure the answer is nucleotides. dna is made up of nucleotides. each nucleotide contains a phosphate group, a sugar group, and a nitrogen base. there are four different nitrogen bases: adenine (a), thymine (t), guanine (g), and cytosine (c). a always pairs with t, and g always pairs with c.