已知数列{a_n}，{b_n}（b_n≠0，n∈N^*）满足b_n+1=$\frac{a_{n+1}·b_n}{a_n+2b_n}$，且a₁=b₁=1．

（1）令c_n=$\frac{a_n}{b_n}$，求数列{c_n}的通项公式；

（2）若数列{b_n}为各项均为正数的等比数列，且b₃²=9b₂b₆，求数列{a_n}的前n项和．

生成氧气的质量为多少克？固体残余物中含有什么物质？质量各为多少？

用所给动词的正确形式填空

    What a day! Yesterday, Ben____(run) to the bus stop. He____(drop) his schoolbag. He ____(pick) it up quickly but he didn't____ (pick up) his homework. He missed the bus so he ran to school.  Tony ____(find) Ben's homework and ____(shout) but Ben didn't____ (hear) him. He ____(carry)Ben's homework to school. There were lots of students at school.

  "I must ____(find)Ben!" said Tony. "BEN!"

  "Tony, you mustn't ____(shout) here."

  "Sorry, Miss Jiang. Can you see Tony?"

  "Yes, he's over there."

  "Thanks. "

  Tony ____(find) Ben and____ (give)him his homework.

  "Thanks a lot, Tony."

  "No problem, Ben."

本文的结构可以划分为三部分，第一部分的意思是____，第二部分的意思是 

____，第三部分的意思是____。