I believe D would be the most reasonable answer for this question given that it has factual information that well suits a topic sentence.
Answer:
The tone or attitude that this idom (Juan is "caught ... with his guard down,") creates <em><u>for the character or audience is the one of "disappointment." </u></em>
<em>It was expected of Juan to always be at alert but he failed hence the reason why the incident happened.</em>
Explanation:
"Many animals die prematurely in zoos because they are exposed to infectious diseases." is the only quote that has anything to do with the claim, "Zoos must improve conditions so that they can meet the health and safety needs of the animals." because it is the only one that has to do with the early of the animals.