The correct answer is B) Countries who created alliances pledged to come to each other's aid.
Alliances serve as a means of cooperation between nations in order to help each other in different circumstances. In this case, one country decides to support others with military support. That is why nations forms alliances, to offer cooperation and help each other in difficult situations. For example, the alliances formed in World War II. The Axis, formed by Germany, Japan, and Itay. Or the Allied Forces, formed by France, Russia, Britain, and the United States.
