题目内容：
回答题Across the Desert
The Sahara Desert is the largest desert in the world. It stretches across Africa from Senegal to Egypt. The Sahara Desert is an unfriendly environment. During the day it's very hot, and at night it's sometimes very cold. It is also difficult to find water in the Sahara.
In 2006, Kevin Lin, Ray Zahab, and Charlie Engle decided to do something very difficult. They made the decision to run across the Sahara Desert—4,300 miles (6,920 km). It seemed impossible to do, but they wanted to try. The three men liked to test themselves, and this would be a very big test.
On the morning of November 2, Kevin, Ray, and Charlie started their trip across the Sahara. Every morning they began running at 5:00. At 11 am they stopped and rested until 5 pm. Then they ran again until 9:30 in the evening. Each day they ran about 40 miles (64 km). Every day it was the same thing. They got up and ran. They listened to music on their iPods, and they ran and ran.
Kevin, Ray, and Charlie needed to eat a lot of food during their trip. Most people need about 2,000 calories of food each day. Kevin, Ray, and Charlie needed between 6,000 and 9,000 calories every day. That's a lot of food! They also needed to drink a lot of water.
The three men had some problems on their trip, and many times they wanted to quit and go home. It was often very hot (140℉/60℃) during the day, and the heat made them sick. their legs and feet hurt. Sometimes it was very windy, and they couldn't see. One time they got lost. But they didn't quit. After 111 days, Kevin, Ray,
and Charlie successfully finished their trip across the Sahara Desert. They hugged each other and put their hands in the water of the Red Sea. Then they ran to a hotel to take a long shower.
The Sahara Desert is not fit for people to live in because of its_____ A．extreme weather.
B．remoteness.
C．vastness.
D．salty water.
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