Final answer:
The shaky start toward union after the Revolutionary War was due to the lack of a common cause, the weakness of the Articles of Confederation, and economic challenges. Therefore, the correct option is A.
Step-by-step explanation:
The disruptive forces that produced a shaky start toward union of the states immediately following the Revolutionary War included the absence of a unifying element of a common cause, as well as other significant issues. After the Revolutionary War, the Articles of Confederation proved to be inadequate in bringing together the states, which operated like separate countries, each concerned about its own sovereignty.
The need for a stronger national government became apparent with uprisings such as Shays' Rebellion, which highlighted the Confederation Congress's inability to maintain peace and harmony. Economic challenges also contributed to the instability, as the central government lacked the power to impose tariffs or regulate commerce, leading to trade disputes and economic recession within the colonies.