What is a weakness of a confederal government system?

A confederate state is one in which its sub-national entities, be they states, provinces, etc., maintain their sovereignty and their right to nullify the laws emanating from the central government. Therefore, the central national government has certain limitations and deficiencies, since it cannot impose its decisions and legislation in the same way that a federal government would, where the states or sub-national entities cede their sovereignty to it.

For this reason, it is necessary that there be in the confederate states a mechanism of communication and political negotiation effective enough to harmoniously amalgamate the sovereignty and interests of each state, and thus facilitate the actions of the central government.

d is the best answer for this question.