The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
The U.S. Constitution solved this problem in that the delegates included the Army clause in the Constitution, that in simple terms says that Congress should have the power to raise and support a national army to defend the country. This clause is on Article I, section 8, clause 12.
Under the Articles of Confederation, the central government was weak. The states were sovereign and could collect money. That is why the delegates met at the Constitutional Convention of 1787 in the city of Philadelphia, Pennsylvania, to create the new United States Constitution and establish the new form of government.