单项选择题
A.≥85%±3% B.≥88%±3% C.≥90%±3% D.≥93%±3%
A.外形区别 B.型号区别 C.耗电量区别 D.氧流量区别
A.7F-1 B.9F-3 C.9F-5 D.9F-3W