The elite have emigrated, what should society do?

The answer is that item A is too absolute. It can be seen from the last sentence of this paragraph that when the tide of elite immigrants arises, it will cause a serious loss of resources and spirit, which will eventually lead to a certain "hollowing out" of society. The phrase "will not constitute a social problem" in item B is inconsistent with the phrase "will not constitute a serious social problem" in the original text. Item C is missing "Once the tide comes ...". "Legal free migration is the embodiment of social openness" shows that item D is correct. So, the answer to this question is D.