human
Question: When the world was very young, people lived in hot places .They didn't live in cold places because they could not keep warm there. At first men didn't know how to make a fire. Sometimes trees were hit by lightning .Then a fire was started .People took some of the fire near their homes. A fire was very important for three reasons. It kept them warm. Wild animals were frightened when they saw it. And when food was cooked, it tasted much better. But men didn't know how to make a fire. When they had a fire, they didn't let it stop burning. If it went out, they couldn't start it again. They had to wait for lightning to start another fire. Sometimes they had to wait for years. Later, they learned how to make a fire. But it was not easy to make something burn . Now we have matches. We can carry them in our pockets and make a fire when we want to. Millions of years ago people didn't live in cold places because  _  .

Choices:
A) they were afraid of cold
B) they didn't know how to keep warm
C) they couldn't make a fire
D) they couldn't find cold places
gpt
The correct answer is 1: they didn't know how to keep warm.