The articles gave the government no separation of powers. The government was too weak, the Articles left much of the power to the states (if I remember correctly, states basically went by their own state constitution). Congress didn't have the power to tax. To change the Articles, it had to be decided unanimously by all states. Also, 9 out of the 13 states had to approve any major law before it was passed and Congress couldn't regulate commerce. There was no president to lead, no established court system, and every state had only one vote in congress.
Basically, the articles created no separate executive department to carry out and enforce the acts of Congress and no national court system to interpret the meaning of laws.
If you are picking from these three options:
it only had the power to raise an army
its members were mostly from the South
it could not levy taxes
it could meet only once a year
I would think this: based on what others have said above, and based on what I have learned, it did not only have the power to raise an army, then mark that out. It's members were not all mostly from the South, they were from everywhere in the U.S.A. It did not only meet once a year, they met more than that, although I'm not sure how much exactly. So that only leaves the choice of that they could not levy taxes. That is your answer right there, and it is only one of the weaknesses of the Articles of Confederation and the federal government. I hope that helped :)