The Nationalist Party, also known as the Kuomintang (KMT), was more popular in China's cities than in the countryside for a few reasons. One reason is that wealthy people who supported the party were concentrated in cities, so the party had more resources and influence there. Additionally, people in the cities tended to be more politically active and aware of current events than people in rural areas. Finally, many poor city dwellers hoped that the Nationalist Party would bring economic change and improve their livelihoods. Therefore, option A is the correct answer. Option B is incorrect because people in the countryside were not necessarily less active in politics, but they may have been less exposed to political movements and parties due to their isolation and lack of access to education and information. Option C is correct but incomplete, as it explains one of the reasons why poor city dwellers supported the Nationalist Party. Option D is incorrect because the Nationalist Party did not threaten to end crop trade with Western nations.