The civil war began when the confederacy fired on Fort Sumter

The Battle of Fort Sumter (April 12–13, 1861) was the bombardment of Fort Sumter near Charleston, South Carolina by the South Carolina militia (the Confederate Army did not yet exist), and the return gunfire and subsequent surrender by the United States Army, that started the American Civil War.

Explanation:

the effect of the ming leaders banning ships with more than two masts was that there was no further construction of ships masts, because there was a surplus. ming emperors disallowed foreign exploration

i believe the correct answer is option b. most eastern european nations joined nato.

though i could be wrong, option d. the eastern european nations were granted complete independence, would be another choice.

hope this ! : )