行场同步信号是在行场消隐期间传送的脉冲信号。场同步信号叠加在

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问题单项选择题

行场同步信号是在行场消隐期间传送的脉冲信号。场同步信号叠加在场消隐信号上，脉冲宽度为（）（2.5个行周期）。

A.4.7us

B.1.3us

C.160us

答案

参考答案：C

填空题

当电力电缆沿铁路桥梁利用电缆槽敷设时，槽内应填层（）或自熄性泡沫塑料垫

单项选择题

Which of the following activities should a 2-year-old child to be able to do()

A．Build a tower of eight cubes.

B．Point out a picture.

C．Wash and dry his hands.

D．Remove a garment.