题目内容：
根据材料，回答问题。Abraham Lincoln was born into a very poor family, but he later became one of the most important1of the United States. In 1860, he was elected to become the 16th president of the Unite States, mainly because of his opposition to 2 By that time, most 3 states had abolished slavery, but the agricultural states in the 4 still wanted slaves to work on their plantations. Mter Lincoln's election, southern states began to secede (break away) from the United States. They based their secession on a doctrine called "states' rights", which gives citizens of individual states the power to nullify (overturn) federal laws.
After Lincoln's inauguration in 1861, he urged all sections of the United States(the Union)to remain united. He used all his powers to avoid a civil war, but his efforts 5. On April 12,1861, the war began with the bombardment of a Union fort, Fort Sumter, South 6 .
By the middle of the 7 War, President Lincoln concluded that the nation could never exist as half-slave and 8 . He issued the9Proclamation, which freed the slaves in the Confederate states. In 1865, the Union soldiers defeated the Confederate soldiers and the war ended on April 9, 10
第1题________
参考答案：
答案解析：