阅读短文，理解题意，然后根据文章内容从A、B、C、D中选出最佳选项。
Aron Ralston is an American man who is interested in mountain climbing. As a mountain climber, Aron is used to taking risks. This is one of the exciting things about doing dangerous sports. There were many times when Aron almost lost his life because of accidents. On April 26, 2003, he found himself in a very dangerous situation when climbing in Utah.
On that day, Aron's arm was caught under a 360-kilo rock when he was climbing by himself in the mountains. Because he could not free his arm, he stayed there for five days and hoped that someone would find him. But when his water ran out, he knew that he would have to do something to save his own life. He was not ready to die that day. So he used his knife to cut off half his right arm. Then, with his left arm, he bandaged himself so that he would not lose too much blood. After that, he climbed down the mountain to find help.
After losing his arm, he wrote a book called Between a Rock and a Hard Place. This means being in a difficult situation that you cannot seem to get out of. In this book, Aron tells of the importance of making good decisions, and of being in control of one's life. His love for mountain climbing is so great that he kept on climbing mountains even after this experience.
Do we have the same spirit as Aron? Let's think about it before we find ourselves "between a rock and a hard place" and before we have to make a decision that could mean lire or death.
．如上所示，明文“4”通过加密加密后得到“3”再发送，接受方通过解密钥解密得明文“4”，问若接受方接到密文为“4”，则解密后得明文是