3. A principal cause for the Russo-Japanese War in 1904 was

1. Disparity in economic ideology

2. Rivalry over China

3. Numerous border disputes

4. A prolonged diplomatic conflict over colonization

5. The Boxer Rebellion

A principal cause for the Russo-Japanese War in 1904 was

Rivalry over China.

Option 2

Explanation:

The principal cause for the Russian and Japanese war was the Chinese rivalry. This has its roots back to the Sino Japanese war. As a consequence of the First Sino Japanese war, the major Peninsular region of China that is Liaodong was annexed by the Japanese.

This annexation was forcefully disagreed by the Europeans and wanted from Japanese to return this Peninsula. Amidst such non favorable circumstances, Chinese gave the region on lease to the Russia. And this leasing from China to Russia created differences between Russia and Japanese.