阅读短文，回答问题。
There is a frog (青蛙). He lives in a well (井) and he never goes
out of the well. He thinks the sky is as big as the mouth of the well.
One day a crow (马狗) comes to the well. He sees the frog and say, "Frog, let's
have a talk." Then the frog asks, "Where are you from?" "I
fly from the sky," the crow says. The frog feels surprised (惊讶) and says, "The sky is only as big as the mouth of the well.
How do you fly from the sky?"
The crow says, "The sky is very big. You always stay in the well,
so you don't know the world is big."
The frog says, "I don't believe(相信)." But the crow says, "You can come out and
have a look by yourself." So the frog comes out from the well. He is very
surprised. How big the world is!
