阅读下面短文，从每题所给的A、B、C、D四个选项中选出可以填入空白处的最佳选项。
A Race Against Death
It was a cold January in 1925 in Nome, Alaska. The town was cut off from the rest of the world due to heavy snow.
On the 20th of that month, Dr. Welch 1 a sick boy, Billy, and knew he had diphtheria, a deadly infectious(传染的) disease mainly affecting children. The children of Nome would be 2 if it struck the town. Dr. Welch needed medicine as soon as possible to stop other kids from getting sick. 3 , the closest supply was over 1,000 miles away, in Anchorage.
How could the medicine get to Nome? The town's 4 was already full of ice, so it couldn't come by ship. Cars and horses couldn't travel on the 5 roads. Jet airplanes and big trucks didn't exist yet.
6 January 26, Billy and three other children had died. Twenty more were 7 . Nome's town officials came up with a(n) 8 . They would have the medicine sent by 9 from Anchorage to Nenana. From there, dogsled(狗拉雪橇)drivers—known as "mushers"—would 10 it to Nome in a relay(接力).
The race began on January 27. The first musher, Shannon, picked up the medicine from the train at Nenana and rode all night. 11 he handed the medicine to the next musher, Shannon's face was black from the extreme cold.
On January 31, a musher named Seppala had to 12 a frozen body of water called Norton Sound. It was the most 13 part of the journey. Norton Sound was covered with ice, which could sometimes break up without warning. If that happened, Seppala might fall into the icy water below. He would 14 , and so would the sick children of Nome. But Seppala made it across.
A huge snowstorm hit on February 1. A musher named Kaasen had to brave this storm. At one point, huge piles of snow blocked his 15 . He had to leave the trail (雪橇痕迹)to get around them. Conditions were so bad that it was impossible for him to 16 the trail again. The only hope was Balto, Kaasen's lead dog. Balto put his nose to the ground, 17 to find the smell of other dogs that had traveled on the trail. If Balto failed, it would mean disaster for Nome. The minutes passed by. Suddenly, Balto began to 18 . He had found the trail.
At 5:30 am on February 2, Kaasen and his dogs19 in Nome. Within minutes, Dr. Welch had the medicine. He quickly gave it to the sick children. All of them recovered.
Nome had been20 .