据报道，科学家发明了一类无色透明塑料、低粘性蜡等物质，在移栽植物时，若将其喷到叶面上，则能结成一层二氧化碳可以通过而水分不易通过的薄膜，能大大提高植株的成活率．这主要是因为薄膜（　　）

大运河沟通南北交通，连接淮河与长江的运河名称是(   )

如果把一只足球看作一个多面体，其中黑色的面（正5边形）共有12块，那么白色的面（正6边形）共有多少块？这个多面体足球共有多少条棱？黑色的边总是和白色的边相接，白色的边一半和黑色的边相接，另一半和白色的相接．

词在填入前需进行词形转换，每个单词只能用一次，每空只能写一词。

    Norman Bethune is one of the most famous ____ for Chinese people. He was not Chinese, but he gave his life to helping Chinese people.

    Norman Bethune was born in 1890, in Canada. He ____ a doctor in 1916. In 1938 he came to China. There were few doctors then, so he had to work very ____. Once, he worked for 69 hours without stopping, and saved 112 people. Although he cut his hand, he did not stop to ____ care of it. In the end, he died from the cut.

    Dr Bethune's work with the Chinese soldiers made ____ a hero in China. He will be remembered by Chinese people for ever.

爸爸的手机，设计于美国，内存卡来自欧洲，屏幕产于韩国，组装于中国，对此现象合理解释是（　　）