18. The Brown decision reversed which of the following earlier decisions? (8.43.1) A. Marbury v. Madison, which established the principle of judicial review
B. Worcester v. Georgia, which established that the federal government rather than
individual states had authority in American Indian affairs
C. Dred Scott v. Sandford, which proclaimed that slaves could not be citizens
D. Plessy v. Ferguson, which endorsed racial segregation laws

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?