Noah Webster's concerns primarily centered around the weaknesses of the Articles of Confederation in fostering unity among the states. The fundamental problem he identified was that "the states would always work in their own self-interest even if it meant harm to the nation as a whole." Therefore, the correct answer would be:
C The states would always work in their own self-interest even if it meant harm to the nation as a whole.
Webster and other founders believed that this lack of a strong central authority could lead to disunity and hinder effective governance.