How/when did the united states officially enter world war ii?

The quote below is an excerpt from the charter of the united nations: "the purposes of the united nations are: to maintain international peace and security, and to that end: to take effective collective measures for the prevention and removal of threats to the peace, and for the suppression of acts of aggression or other breaches of the peace, and to bring about by peaceful means, and in conformity with the principles of justice and international law, adjustment or settlement of international disputes or situations which might lead to a breach of the peace . " source:this section implies that the united nations is prepared to do what to keep world peace?

Europe and asia are divided by a. the alps c. the pyrennes b. the northern european plain d. the ural mountains select the best answer from the choices provided a b c d

What are three supporting points as to why opium was wrong in the chinese trade? why should it have stopped? (opium wars)