Given the question: Write a multi-choice question for the following article, with the given choices and answer: Article: Fat and shy, Ben Saunders was the last kid in his class picked for any sports team. "Football, tennis, cricket -- anything with a round ball, I was useless," he says now with a laugh. But back then he was the one always made fun of in school gym classes in Devonshire, England. It was a mountain bike he received for his 15thbirthday that changed him. At first he went biking alone in a nearby forest. Then he began to ride the bike along with a runner friend. Gradually, Saunders set up his mind on building up his body, increasing his speed and strength. At the age of 18, he ran his first marathon. The following year he met John Ridgway and started to work as a teacher at Ridgway's school of adventure in Scotland, where he learnt about Ridgway's cold--waterexploits. Greatly interested, Saunders read all he could about North Pole explorers and adventures; he decided that this would be his future. In 2001, after becoming a skillful skier, Saunders started his first long--distance expedition towards the North Pole. It took unbelievable energy. He suffered frostbite, ran into a polar bear and pushed his body to the limit, pulling his sled up and over the rocky mountains. Saunders has become the youngest person to ski alone to the North Pole, and he's skied more of the North Pole by himself than any other British man. His old playmates would not believe the change. Options: A He decided to build up his body. B He met John Ridgway in Scotland. C He worked as a teacher at school. D He took an adventure to the North Pole. Answer: D He took an adventure to the North Pole. Question:
The answer is:
What did Saunders do in 2001?