Final answer:
China was vulnerable to Europeans' desire for expansion because it had fallen behind in the development of military technology.
Step-by-step explanation:
China was vulnerable to Europeans' desire for expansion because it had fallen behind in the development of Military technology. The Europeans had more advanced weapons and military tactics, which gave them an advantage over China. Additionally, the Qing Dynasty did not produce heavy military weapons as early as the Europeans, making it difficult for China to fend off invasions.