题目

Living in the central Australian desert has its problems, _____getting water is not the least. A. as   B. of which    C. whose   D. for what 答案：B已知二氧化硫的化学式为SO2，求（1）二氧化硫的相对分子质量（2）二氧化硫中各元素质量比（3）二氧化硫中硫元素的质量分数（4）64克中二氧化硫中硫元素的含量．