阅读下面短文，从每题所给的A、B、C、D四个选项中选出最佳选项。Doorbells are the bells（铃）for people to ring at a door. When someone hears it, he or she can open the door. Do you know that you can ring a doorbell for fish, too?
Every spring, millions of fish migrate（洄游）along the river in the city to find better places to lay eggs. But in the river, there are many locks（水闸）. They stop fish from swimming through. Weerd Lock is in Utrecht, the fourth largest city in the Netherlands. When fish get there, they have to wait a long time before the lock opens for boats to pass through. The lock keeper there is glad to open the lock for fish, but he cannot tell when fish want to get through. So in 2021, Mark a scientist, came up with a good idea to help solve this problem— by using the fish doorbell.
Under the water near the lock, there's a camera. People from around the world can visit a website to see fish through the camera. When you see a group of fish waiting, you can ring the doorbell on the screen. And when the lock keeper notices it, he will open the lock for the fish.
In its first spring season in 2021, people around the world rang the fish doorbell more than100,000 times. If you want to join them to help fish, visit the website and ring the fish doorbell next spring!
