Maybe put it in parenthesis or maybe wait until the next paragraph. I'm not sure it all depends on your teacher.
Explanation: The rule for indefinite article usage is as follows: Use before nouns (or adjectives) that start with a consonant sound. Use before nouns (or adjectives) that start with a vowel sound.
I don't really k but i think it's D.to purchase one of their milk cows or C.<span>to warn the family about hydrophobia</span> but i would choose one of those two.
or maybe it's supposed to be D. to purchase a milk cow or something.
hope i helped :)
