A:remaining to be done, stay
B:remained to be done, stayed
C:remaining to do, to stay
D:remained to do, staying
调查某城市的空气质量,应选择____ (填抽样或全面)调查.
若实数范围内定义一种运算“﹡”,使a*b=(a+1)2﹣ab,则方程(x+2)*5=0的解为( )
下列类别物质的组成中一定只含有两种元素的是( )