单项选择题

A、A
B、B
C、C
D、D

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单项选择题

拉曼位移是指散射光频率与激发光频率之差，其大小与入射光波长有关。（）

A．对
B．错

单项选择题

“In some types of precast concrete, such as the railway sleepers, strengths ranging from 40-60 N/mm2 at 28 days are obtained with rich mixes, having a low water cement ratio.” What does the underlined word mean?
A、Someone who sleeps.
B、Sleeping car.
C、Railroad tie.
D、A type of pajama.