①Na₂SiO₃②CaCO₃③CaSiO₃④SiO₂⑤Na₂CO₃⑥CaO．

将稍微有些凹陷的乒乓球放人热水杯中，乒乓球会____ ，这是因为____ 。

完形填空。

   1! My name  2Alice. I'm fourteen  3  . I like playing Volleyball  4 going to the cinema. My favourite5  is Christmas.

    This is my friend Joe. He's fifteen. He   6  like playing sport. He can7  English and he likes Maths. He wants8   everything about it.

    This is my cousin. She is thirteen.   9 favourite sport is skating and she can skate very   10   . She likes music. She says it's exciting.