极板硫化产生的粗晶粒硫酸铅导电性能很差，正常充电很难还原为（）和海绵状铅。
A.硫酸
B.硫酸铅
C.蒸馏水
D.二氧化铅
参考答案：D
Students are required to go out in couples, especially in the evenings, with friends ______ they get into trouble.
A．even if
B．if only
C．in case
D．when
膝反射消失时禁用
A．硫酸镁B．缩宫素C．麦角新碱D．呋塞米E．甘露醇
