What major concern arose regarding the German population in Tanganyika?

The correct answer highlights a significant concern at that time about the German population in Tanganyika, which was their potential to heavily influence the local dynamics due to their larger numbers compared to other European communities. This demographic factor raised alarms among local authorities and other European settlers, as a significant population of Germans could lead to increased influence in political, economic, and social structures.

In terms of context, while other concerns may have existed regarding German sentiments towards their homeland or their economic activities, the predominant worry was their sheer number, which could make it difficult for other factions to assert control or balance the social order in the region. This abundance of Germans in Tanganyika could create a platform for unifying efforts that might lead to political shifts or alliances that wouldn't be favorable to British interests in the area.