题目

Housewives are working hard to clean grease(油腻) at every corner of the kitchen with their hands. Now, American scientists have invented a new kind of special _____. It can help housewives say goodbye to the ____work in the kitchen. After spraying(喷) some of the water on the kitchen table and floor. people can easily______the dirty points and areas.Jeffrey Youngblood, a doctor of Purdue University, led his team to study ______to make the dirty things easily cleaned for many years. Recently he _____his study results to the world-Self-cleaning water. There are some chemical(化学的 ) thin已知Cl元素只有2种天然核素35Cl和37Cl，且知Cl元素的近似平均相对原子质量为35.4。试求天然存在的这两种元素的原子个数比。