An (blank) is an affix added to certain classes of words to change their grammatical meaning.

a.) inflection
b.) apology
c.) anology

I would say A. Inflection because an inflection is a change to the form of a word to change its grammatical function

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.