I know what a composition of 400 words means.

Growing up, there are many small question marks in my mind, such as: Why didn't the tumbler fall? Why can earthworms live into pieces? Why can the little gecko fly over the eaves and walk over the wall? Why can a large ship weighing thousands of tons sail at sea? ......

Among them, I am most interested in: How do bats find their way? The problem was finally solved that time.

It was a summer night and it was very hot. The adults went outside to enjoy the cool, and my father and I ran out together. I only felt mosquitoes flying in front of me, so I picked up a stick and dangled it over my head. Unexpectedly, many mosquitoes were shot down.

Just as I was about to stop, a black thing the size of a fist flew over and scared me. I looked intently and saw that it was a bat. It circled over my head several times, ready to fly away. I chased it with a stick for a while. I see a big tree in front of me. The bat wriggled and quickly ran away. I don't know, but I heard a bang. I had a close contact with Dashu.

I thought: How can bats have such good eyesight? So, I went home to check the information and found an encyclopedia of biology to read.

When I saw the "Ultrasound" page, I found that there was an introduction of bats. The book says: Bats have very poor eyesight and can't see anything at night. They are blind at all, and their eyesight is not very good during the day. It can be said that our human vision is 5-6 times that of theirs.

After reading this, I wonder: in this case, how did it see the tree just now?

In order to solve this mystery, I continued to look down.

Finally, I understand that bats are located by ultrasound. Ultrasound can help them find obstacles ahead and measure the distance, so that they are not easy to crash at night. Humans have also discovered many things according to the ultrasonic waves of bats, such as radars and ultrasonic planes. ......

Later, I also learned that dolphins also have ultrasonic waves. They rely on ultrasound to find fish hidden in sand and stones on the seabed. Dolphin ultrasound can also treat people, help eliminate toxins in bones and promote metabolism.

I finally understand the secret of bats finding their way at night and the many uses of ultrasound. I also know that books are our mentors and friends and valuable wealth. We should read more intentional extracurricular books to enrich our knowledge and broaden our horizons.