Why is D wrong? Thanks

Hi Jing Jing, thanks for the question. The economists' assertion is that trading goods or services produced predominantly by an urban population in order to obtain the agricultural products that were previously produced domestically would address the problems resulting from increased urbanization. C is correct because scarcity of agricultural products being a central element of many problems created by urbanization would be positively impacted by the economists' assertion. D is incorrect because whether these problems are caused by trade imbalances or not is not the issue under question. We are not trying to determine a root cause for problems, we are trying to find something that will support the economists idea. I hope this helps. Please let me know if you have any other questions.