Read the article and select the best answer. Article: The world lost one of the most respected leaders. Nelson Mandela, the former   South African president, passed away on Dec. 5, 2013. The whole world felt sorry about the death of Mandela, a great man of history. Mandela is mostly remembered for his efforts to end apartheid  in South Africa. Mandela was born in 1918. In South Africa, there are both black and white people. But at that time, Black people couldn't live or travel where they wanted. They didn't have the right to vote, either. Mandela didn't think that was right. He organized many activities against it, but he was sent to prison for 27 years. Under international pressure, the government set Mandela free in 1990. Great changes in the law began to end apartheid. At that time, Mandela chose to forgive his enemies. He shook hands with the people who wanted him dead. He also encouraged black people to forgive the whites. Because of his forgiveness, Mandela is remembered as a moral model  by the whole world. In1993,Mandela won the Nobel Peace Prize. A year later, he became the first black president of South Africa. Both black people and white people voted. Apartheid ended. In 1999, Mandela left office at the highest point of his power. Question: Mandela was sent to prison for 27 years because he   _  . Options: A: chose to forgive his enemies. B: encouraged black people to forgive whites C: shook hands with enemies D: organized many activities against apartheid

D