—That was a difficult question, but Mary still ______ to work it out.A. did B. f

—That was a difficult question, but Mary still ______ to work it out.A. did B. f

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轨枕按其制作的材料不同分为()和钢筋混泥土枕两种。

轨枕按其制作的材料不同分为()和钢筋混泥土枕两种。

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()防护自动闭塞区段的闭塞分区和非自动闭塞区段的所有区间。A.进路信号机B.进站信号机C.出站信号机D.通过信号机

()防护自动闭塞区段的闭塞分区和非自动闭塞区段的所有区间。A.进路信号机B.进站信号机C.出站信号机D.通过信号机

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CTCS-2级区段,()产生运行许可并连续向列车传送。A.轨道电路B.有源应答器C.无源应答器D.LEU

CTCS-2级区段,()产生运行许可并连续向列车传送。A.轨道电路B.有源应答器C.无源应答器D.LEU

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—They have learned about ______ in recent years.A. several hundreds English word

—They have learned about ______ in recent years.A. several hundreds English word

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