Read the following article and answer the question. Article: Alexander von Humboldt was born in 1769 in Berlin, Germany. As a young boy, he wanted to learn about the world. Humboldt followed his dream. In 1799, he traveled with a friend to Central and South America. On their trip, Humboldt and his friend saw and did many things. They sailed down the Amazon River. They watched dolphins play in the ocean. They explored the rain forest and climbed mountains and volcanoes. They were able to make the first maps of the northern part of South America. Humboldt set a world record for mountain climbing. He also made a discovery. During his climb, Humboldt became very sick. He found out that the higher he climbed, the less oxygen there was in the air. This made it more difficult to breathe. Later, this became known as mountain sickness. Science was another part of Humboldt's interests. He wanted to write about all of the new things he saw. He described the new plants, animals, and rocks which had never been seen by scientists before. Humboldt also studied the way of life of the local people. He learned how the native people along the Amazon River used plants in their daily lives. For example, they used a strong poison from a vine to make poisoned arrows. The natives used these arrows for hunting their food. The Amazon Indians also used a native plant to treat malaria , a serious illness. The plant grew wild, but after it was dug up, it was never replanted. Humboldt warned the natives that the plant was in danger of dying out. He looked for ways to preserve the plant and to make it grow strong. Although Humboldt took many risks during his trip, he lived to be 90 years old. In his lifetime, he made many discoveries and shared them with the world. As a tribute to Humboldt, there are rivers and mountains named after him. Question: What do we know about mountain sickness? Answer:
Answer:
It mainly influences one's breathing.