某可燃冰[CH4·nH2O]完全燃烧后生成的二氧化碳和水的质量比为11比27，则该可燃冰中碳氢元素的质量比为（　　　　）.

UNICEF () money to () education for poor childrenA. collects ,providesB. raises ,giveC. collect , givesD. raises ,provide

三角形一边上的中线与三边的长度之间有什么数量关系？该怎样证明？

1.选择Teachers often ask us () make any noise in class.A. to try not toB. not try to notC. not to try toD. try not to2.填空She is one of the ()(success)businessmen in the world.请说明理由.谢谢.

关于"越过"的词的区别cover,clear,spring.