阅读下面短文，从短文后各题所给的A、B、C、D四个选项中，选出可以填入空白处的最佳选项。
One day while Logan was returning from school, he saw an old man on the ground unconscious（无知觉的） while some others were calling his name. It seemed that the old man 1 be in a serious situation. Logan rushed towards the old man without a second thought. 2 just before few weeks, he had his first-aid class at school about how to do CPR（心肺复苏） when someone is in danger.
Logan at once got into the situation. He listened to the old man's breathing and 3 his pulse （脉搏） and found it weak and his body 4 . He thought the old man probably had suffered a heart attack. He asked people around to give him some 5 and carefully made the old man lie down on the ground, then he began doing a hand CPR. He 6 down on the man's chest regularly, while asking another man to 7 mouth-to-mouth.
At the same time, someone else called the emergency （急救） services. Logan continued to do the CPR for several minutes and 8 to save the life of the old man. During the process, the old man began to 9 again, which gave Logan the 10 to go on.
Once the emergency personnel came, they thanked Logan and took the old man to the 11 hospital. He didn't tell his name to the old man's friend but they took a photo of him. It was Logan's quick 12 and first-aid knowledge that saved the old man's life.
After Logan got home, he told his parents what had happened, but they didn't treat it as anything 13 and they said he was a wam-hearted young man.
A few days later Logan had 14 about the event and lived his life as before. However, the old man who had been saved has kept him in mind. From Logan, we know that everyone's action can play a 15 when others are in a serious situation.
