I want to know the answer to the following question:
What was the main problem the Qing had in preventing invasion from Europe?
All the background I'm provided with is that "Historians have judged the Qing dynasty's vulnerability and weakness to foreign imperialism in the 19th century to be based mainly on its maritime naval weakness while it achieved military success against westerners on land, the historian Edward L. Dreyer said that "China’s nineteenth-century humiliations were strongly related to her weakness and failure at sea.". Is that enough to answer the question?
Answer: yes