单项选择题
A.<10% B.在10%~12%之间 C.=12% D.>12%
A.硬盘 B.软盘 C.RAM D.ROM
A.HI>HBr>HCl>HF B.HF>HI>HBr>HCl C.SiC>SiCl4>CaO>MgO D.SiC>CaO>MgO>SiCl4