C is the answer some may say otherwise but the key word(s) that make it an opinion to be argued are; inadequate. That word is a big red flag showing its an opinion. not all people think Rhodes so called small gestures are inadequate.
Answer is a) a
Reason. Milk is a drink for children.
It’s not “an” drink for children or “the” drink for children. Unless there is an article somewhere you didn’t post I don’t know what d) no article means.
What is the writer attempting to persuade you of concerning the captivity of marine animals