What was a significant risk perceived by the U.S. regarding Japan in the early 20th century?

The correct answer highlights a significant concern for the United States regarding Japan's rising influence and military capabilities during the early 20th century. Specifically, the apprehension about a military alliance between Japan and Britain reflected fears of a powerful coalition that could challenge U.S. interests, especially in the Pacific and Asia. This concern was rooted in Japan's growing naval strength, which was highlighted by its victory in the Russo-Japanese War (1904-1905).

The potential for Japan and Britain to cooperate militarily raised alarms about a shift in the balance of power, particularly as both nations had interests in Asia. The U.S. was concerned that such an alliance could lead to increased Japanese aggression and expansion, threatening American territories and influence in the region. This context is crucial for understanding U.S. foreign policy decisions during this period, including the establishment of the Open Door Policy to ensure equal trading rights in China and its subsequent military preparations in the Pacific.

In contrast, the other options do not accurately reflect the central concerns of U.S. policymakers at the time. The idea of a Japanese empire in Africa was not a significant point of contention as Japan focused on its interests in Asia. While Western European nations did have interests in Asian affairs, the specific concern