从C、H、O三种元素中，选择适当元素，组成符合下列要求的物质，将其化学式填在横线上：①固体可用于人工降雨的是____；②“西气东输”的主要气体是____；③用煤炉取暖时易发生中毒，主要是由于室内____排放不畅引起的．

3.14×12＝（   ）

阅读下列材料：

材料一：“大唐国者，法式备定，珍国也，常须达。”

──《日本书记》

材料二：天竺戒日王对玄奘说：“弟子闻彼国有《秦王破阵乐》歌舞之曲，未知秦王是何人？复有何功德，致此称扬？”

材料三：从对外关系上说，隋唐宋元都居于主动地位，明清时期的对外关系显然逆转了……明朝时，倭寇沿海骚扰，清朝时统治者认为“天朝物产丰富……原不藉外夷货物以通有无。”，于是清政府对世界形势一无所知。

根据短文理解，从A、B、C、D四个选项中选择最佳的一个答案填空。
    Sometimes, I want to know whether there is any love between my parents. Every day, they are 1 trying to make money. They don't act romantically（浪漫地）the way couples(夫妇)do in books 2 on TV. They never say “I love you" to each other. It's not their 3.
    One day, my mother was sewing(缝) a quilt. I sat down next to 4. “Mom, I have a question to ask you," I said after a while. “What?" she asked, still working. 
   “Is there love 5 you and Dad?” I asked her in a very low 6.
    She stopped her work and 7 her head. Then she bowed（低下）her head and went on sewing.
    I thought I had hurt her. At last I heard my mother say, “Susan, look at this thread（线）Sometimes it 8, but most of it disappears in the quilt. It makes the quilt 9. If life 10 a quilt, then love should be a thread. It can 11 be seen anywhere, but it's really there.”
    I listened carefully but I didn't understand her 12 the next spring. My father suddenly got sick. My mother had to stay with him in the 13 for a month.
    After they got back, she helped my father walk slowly down the road every day. My father had never been so weak.
  “Dad,  14 are you feeling now?" I asked him one day.
  “Susan, don't worry about me,” he said gently “I just like 15 with your mom.” Once I thought love meant flowers, gifts and sweet kisses. Now, I know that love is the thread that holds a family together.

10.已知{a_n}是正数组成的数列，a₁=1，且点( ，a_n+1)(n∈N^*)在函数y=x²+1的图象上.