单选题：It remains a puzzle about why our outermost planet exists.

题目内容：

It remains a puzzle about why our outermost planet exists. A．problem
B．mystery
C．question
D．point

参考答案：

答案解析：

It is postulated that population trends have an effect on ec

It is postulated that population trends have an effect on economic fluctuations.

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All the pupils seem to be very cheerful.A．happy B．healthy C．naughty D．busy

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They're petitioning for better facilities for the disabled on public transport.A

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在采用实测法进行施工现场的质量检查中，“套”是指以方尺套方，辅以塞尺检查，通常用“套”的方法进行检查的项目有（　　）。A．门窗口及构件的对角线 B．踢脚线的垂

分类：理工类题型：单选题