北回归线自西向东穿过我国的四个省区是（    ）

美国”9.11”恐怖袭击事件中，毁坏的建筑物散发出大量的石棉，人吸入石棉纤维易患肺癌，石棉是硅酸盐矿物，某种石棉的化学式为：Ca₂Mg_xSi_yO₂₂（OH）₂，该化学式中的x，y的值分别是（　　）

    David is from America. He and his family____(have) different plans for the coming holiday. David likes China very much and he____ (go) to Beijing last year. But he wants to know more about Chinese culture so he____ (visit) Beijing again. This time he is going to the Palace Museum. There____ (be) many interesting things about Chinese culture there. He____ (want) to take lots of photos of the things in the Palace Museum. He____ (show) them to his friends. David's father ____ (read) many books about Japanese history three months ago. He thought some things in Japan were interesting. He____ (take) a trip to Japan. David's mother didn't know where to go at first. At last she ____ (decide) to go to Singapore. She likes the climate (气候) there. What about David's sister? She ____ (stay) at home and do her homework.