Mum_______________ since 6 am.She_______________ over 400 km. (drive)
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We_______________ for an hour.We_______________ more than 2 km! (swim)
Mr Bosworth_______________ more than 2,000 children.He_______________ since he was 22. (teach)
They_______________ apples all day.They_______________ hundreds! (pick)
在杂质半导体中多子的数量与( )有关。
A. 掺杂浓度
B. 温度
C. 质量
D. 体积
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