Why is A correct? Why is D incorrect?

Hi Ryan, thanks for the question. We need to parallel the conditional reasoning in this short passage. The conditional diagrams in this passage look like this: Premise 1: People who are indifferent to their environment - > pollution is a problem (A - > B) Premise 2: Pollution - > Nature's balance is harmed (B - > C) Conclusion: People who are indifferent to their environment - > Nature's balance is harmed (A - > C) Now let's find the answer choice which parallels this reasoning. Answer choice A does the exact same: A - > B and B - > C, therefore, A - > C Answer choice D on the other hand does the following: A - > B and B - > C, but then it incorrectly (and most importantly, differently) concludes the following, therefore C - > A. It reverses the conditional diagram. I hope this helps. Please let me know if you have any other questions.