555精密定时器是由端子分压网络、两个电压比较器、双稳态多谐振荡器、放电晶体管和()组成。
A. 射极输出器
B. 功率放大器
C. 推挽输入级
D. 推挽输出级
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填写工作票时要字体规范，不得涂改和不得用()填写。
A. 钢笔
B. 圆珠笔
C. 铅笔
线绕式异步电动机串级调速有哪些优点？适用于什么场合？
A.Houses are much more quiet.B.Houses provide more privacy.C.They want to have more spa
A. Houses are much more quiet.
B. Houses provide more privacy.
C. They want to have more space.
D. They want a garden of their own.
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