阅读下面短文，掌握大意，然后从A、B、C、D四个选项中选出一个最佳选项。
The sun is shining and the birds are singing around. On such a 1 morning, a UFO lands in a forest. A boy called Bill is just watching it behind a tree.
Suddenly, a tall alien* comes out of the UFO. He wears a silver suit and starts picking up 2 . One by one, he takes photos of them with a camera. When he finishes, he puts the flowers into a large box.
The alien thinks he sees something move and asks, "Is anybody there?" Bill doesn't answer.
The alien 3 the looker and sees the boy behind the trees. "Oh, there is someone. Hello!" the alien says, "It's all right. You can come closer."
"What are you doing?" Bill asks.
"I'm 4 flowers," the alien says.
"Flowers? For what?" asks Bill.
"I'm going to take them back to my planet*," says the alien.
"Aren't there any flowers on 5 ?" asks Bill.
"No, our planet doesn't have flowers for a long time." The alien says 6 , "We have too much litter, we cut down too many trees, 7 now it's like a desert*. There is almost no water any more. All of the flowers and trees that lived on our planet are gone."
"That's terrible," says Jim "Is anyone doing 8 about it?"
"Yes ... That's 9 I'm here and we want to find plants from other planets. We use them to learn about water. I believe someday water will come back to our planet."
"Wow," Bill said. "What's the name of your planet?"
It's called Rozul," the alien says, "Long ago, it was very beautiful. If we work hard, someday Rozul will be 10 again." And then the alien goes back to the UFO. Bill says goodbye as the UFO slowly goes up into the air and flies away.
