题目

In Canada and the United States, there is a new group of children called “satellite kids”, who live in one place but whose parents live in another place. Asians are immigrating (移民) to Canada and the United States in larger numbers than ever before. Most Asians immigrate because they believe that they can give their children a better education in the West. In Asia, especially in China, Japan, and Korea, it is difficult to go to university. Students must first pass the strict national examination. However, in Canada and the United States, it is easy to go to university, and anyone石膏硬化的变化是（    ） A．由CaSO4变成CaSO4•2H2O B．由CaSO4•H2O变成CaSO4 C．由2CaSO4•H2O变成CaSO4•2H2O D．由CaSO4•2H2O变成2CaSO4•2H2O