Not sure if D is rifht

using its large navy to capture German colonies in the Pacific and Indian oceans

Explanation: You're right

might be agreeing to participate ethically with other european nations in the slave trade

or notifying other european nations when taking possession   of african territories

answer is b.

  it is always the best policy to have good communication and good relations between individuals and, specially, between leaders of the countries. for this purpose, among others, there is a common place, the united nations, where the representants can present his and learn about the other country's policies.