Today, over six billion people live on the planet. This means that there are very few places on Earth with no people. One place that has very few people is at the bottom of the Earth. In Antarctica, the icy continent surrounding the South Pole, you will not find anyone who lives there all the time. First, Antarctica is the coldest place on Earth. For example, it can be -l30degC in the winter. Humans cannot live in this kind of environment. Because it is so cold, very few plants or animals live there. This means there are no farms and no places to find wild plants or animals to eat. Second, Antarctica can be dangerous. Many people think that it is safe to travel to Antarctica in the summer months when it is warmer. However, Antarctica is mostly ice, so when it's summer, the ice melts. When the ice melts, the ice can break. So, people cannot travel around Antarctica during the summer. If the ice breaks, they could fall into the water and die. Another serious problem in Antarctica is the sun. Because Antarctica is mostly ice, there are no trees so there is no shade. Also, the ground is mostly white ice so the sun bounces off   it. The light from the sky and the light from the ground can burn people's skin and hurt their eyes. People must be very careful in this situation. For example, they must wear sunglasses to protect their eyes. They must also cover their hands and faces all the time. Although Antarctica is a tough place to live, explorers have discovered coal in Antarctica. This leads them to believe that Antarctica at one time was a land of swam   and forests. When is the most dangerous time to travel around Antarctica?
In spring. In summer. In autumn. In winter.
Question: Today, over six billion people live on the planet. This means that there are very few places on Earth with no people. One place that has very few people is at the bottom of the Earth. In Antarctica, the icy continent surrounding the South Pole, you will not find anyone who lives there all the time. First, Antarctica is the coldest place on Earth. For example, it can be -l30degC in the winter. Humans cannot live in this kind of environment. Because it is so cold, very few plants or animals live there. This means there are no farms and no places to find wild plants or animals to eat. Second, Antarctica can be dangerous. Many people think that it is safe to travel to Antarctica in the summer months when it is warmer. However, Antarctica is mostly ice, so when it's summer, the ice melts. When the ice melts, the ice can break. So, people cannot travel around Antarctica during the summer. If the ice breaks, they could fall into the water and die. Another serious problem in Antarctica is the sun. Because Antarctica is mostly ice, there are no trees so there is no shade. Also, the ground is mostly white ice so the sun bounces off   it. The light from the sky and the light from the ground can burn people's skin and hurt their eyes. People must be very careful in this situation. For example, they must wear sunglasses to protect their eyes. They must also cover their hands and faces all the time. Although Antarctica is a tough place to live, explorers have discovered coal in Antarctica. This leads them to believe that Antarctica at one time was a land of swam   and forests. When is the most dangerous time to travel around Antarctica?
A. In spring.
B. In summer.
C. In autumn.
D. In winter.
Answer: