13. The main idea of the second paragraph (the highlighted sentence) is that:
Your Answer is
Correct Answer is D
Explanation
Item D: The topic sentence is the last sentence, we cannot lose the taxonomy because it is so important to our understanding of the world.
Item A: There is no mention of the decline in the number of experts.
Item B: No mention of natural history.
Item C: "Classification is not an obscure science because it is widely studied", the error is because the focus of this paragraph is not whether it is difficult to understand, but to emphasize that classification is very important.