A:2NaW+Z2===2NaZ+W2
B:2NaX+Y2===2NaY+X2
C:2NaY+W2===2NaW+Y2
D:2NaZ+X2===2NaX+Z2
只用水不能区分各组物质(物质均为固体)的是( )
—Were you at home yesterday?
—No, I________. I was ________ school.