What was one of the conditions for British Columbia joining Confederation?

British Columbia agreed to join Confederation primarily under the condition that a railway would be constructed to facilitate transportation across the new province. The promise of a transcontinental railway, specifically the Canadian Pacific Railway, was crucial in persuading British Columbia to join the Confederation in 1871. This railway was intended to connect British Columbia with the rest of Canada, helping to promote trade, migration, and economic development, while also ensuring that the distance from the eastern provinces didn't hinder integration into Canada.

The other options, while they may contain elements related to British Columbia's interests, do not reflect the primary condition that was central to the agreement for joining Confederation. The railway played a pivotal role not just in uniting the provinces but also in addressing concerns over isolation and access to markets, making it a cornerstone of British Columbia's entry into Confederation.