单极性不归零码(NRZ),就是指信号“1”有脉冲,信号“0”无脉冲。其占空比为50%。( )
第2题
Why didn't he go to the rich man's house at last?
A.He couldn't cross the river.
B.It was too late.
C.He found some other good food.
第3题
听力原文:(A) The bridge crosses the stream.
(B) The bridge is washed out.
(C) The river's too wide to cross.
(D) The road goes through the river.
第4题
There is a wood bridge ______the river.
A. above
B. on
C. over
D. up
第6题
They are building a bridge __________ the river.
A. through
B. across
C. on
第8题
A.at the normal condition
B.at the common situation while navigating
C.from the position from which ships are normally navigate
D.at the safe maneuvering condition for ships
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