根据短文内容, 完成下列任务。

    One fresh sunny day, while I was swimming in the water, I felt something special going through my gills(鳃).It was a different kind of water. I also found many of my friends became sick. Some of them were dying. I was starting to worry because I didn't want to get sick or die. I was also thinking about what I should do to save my friends, so I decided to do some research for my underwater life.

    My research started. At first, I noticed there were many bottles, cans and other kinds of rubbish in the water. Then I went on… I got closer and then I tasted many different kinds of liquid(液体).(A)To my surprise, I noticed a man pouring some liquid into the water. Others also saw him doing so and they decided to follow him. I hated it! I wish I could have told them that it was killing us!

    I think it is so stupid for people to do this to the earth that they are living on! I can't understand (B)      they are doing this. Humans should stop throwing waste into the lakes or rivers. I want to have a normal life with my friends. People should stop being so selfish and care about the environment. If they do that, everyone will be fine and will have nothing to worry about. I suggest they follow my words. If so, I believe everyone will be able to live a happy life.

下列各式中，正确的是（　　）