What is the relationship between the subject ( main topic) and the writer?​

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.

The girl walked up to the dog. of course she was only three years of age so she had no knowledge of what she was doing. she walked up to the wild beast, without considering the consequences. but she would find out soon. she held out her hand to touch the mangled canine. snap. the toddlers hand was soon covered in a red liquid.