从H、O、S、Na四种元素中,按指定化合价(H+1、O﹣2、S+4、Na+1)两种或两种以上的元素,最多可以组成化合物的种数是( )
A:8种
B:7种
C:6种
D:5种
Mr. Lee for Taiwan for his holidays the day after tomorrow.
不等式3≤x-2<9 的解集为____
—_________ meat do we need every day?
—We need a little.