题目

       Heavy downpours last month in Rhode Island led to widespread flooding, causing millions of dollars in property damage and leaving thousands homeless. The flood waters also poured vast amounts of raw sewage(未经净化的污水) into the rivers and streams that flow into Narragansett Bay.        It sounds like the makings of an environmental nightmare. But in fact it’s just the opposite. To scientists’ delight. The sewage-loaded floodwaters have caused a well-timed growth of phytoplankton. The microscopic creatures that form the foundation of marine(海洋的) food chai下列各组物质在加水充分溶解后过滤，滤纸上有两种不溶物的一组是（ ）A．CaCl2、Ca（N03）2、Na2C03B．CuS04、Cu（N03）2、Ba（OH）2C．KCl、Ba（N03）2、NaOHD．FeCl3、KOH、BaCl2