A. How the precipitation or runoff is actually formed. B. How the table salt we use is obtained. C. The processes that cause a change in oceanic salinity. D. The processes the dissolved materials are left behin 参考答案:C 答案解析:主旨题。根据文章内容,我们知道文章主要讲的是引起海水含盐量变化的三个过程,所以选项C是正确答案。