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问题 单项选择题

关于焦点的叙述正确的是（）

A.电子在阳极上撞击的面积是有效焦点

B.实际焦点在X线中心方向的投影是主焦点

C.有效焦点标称值是以mm为单位

D.实际焦点包括主焦点和副焦点

E.有效焦点是圆形

答案

参考答案：D

单项选择题

According to International Financial Reporting Standards, which of the following is one of the conditions that must be met for revenue recognition to occur（）

A. Costs can be reliably measured.

B. Payments has been partially received.

C. Goods have been delivered to the customer.
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问答题 简答题

哪些情况下可使用警棍？使用限度是如何规定的？
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