A

    Last week, 36 students in Linyi, Shandong Province, wore beautiful clothes in a show. Their clothes were made of all kinds of waste things.

    The show gave the students a chance to make clothes with their own hands. It also helped them learn to make good use of waste things.

    "We hope to save energy. Our world is short of energy, so I don't want to throw old things away," said Xie Jing at Linyi Art School. Xie had more than 20 CDs from her family and friends. "Though the CDs are old, I look very cool in them!" she said.

    Wang Dandan, a student from the same school, looked like a farmer in her straw (稻草) coat and hat. She picked the straws from the fields and put them all together. "I want to show what people wore in the past," she said.

    Du Yue made clothes like astronauts' clothes. Her clothes were white. When she walked, she tried to be slow. It looked like she was walking on the Moon. "I wish that I could walk on the Moon!" she said.

Li Qiang is_____ honest boy. He wants to be_____useful person when he grows up        

已知{f_n（x）}满足f₁（x）= $\frac{x}{\sqrt{1+x^2}}$ （x＞0），f_n+1（x）=f₁f_n（x），

①同种元素   ②同种原子   ③质子数相同   ④质量数相同   ⑤互为同位素．