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问题 单项选择题

半功率点宽度是指场强方向性图中（）时的两个方向的夹角。

A、场强为最大值的0.707

B、功率密度降到最大值的0.707

C、场强为最大值的0.505

D、功率密度降到最大值的0.505

答案

参考答案：A

判断题

水准仪的原理是借助水准仪提供的水平视线，首先配合水准尺测定地面上两点间的高差，然后根据已知点的高程来推算出未知点的高程。( )
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单项选择题

A parent reports that his 2-year-old child often fails when running. The nurse interprets this as indicating which of the following as a normal aspect of a toddler's vision

A．Near-sightedness.

B．Far-sightedness.

C．Binocular vision.

D．Strabismus.
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