If you have been invited for a meal._______,________, or a small gift are all appropriate. A ________ note or telephone call after the visit is also considered polite.
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When inviting guests for dinner in Britain, the hostor hostess may serve the food in several ways such as ________ style, ________style and ________ style.
In Britain, it is wise to telephone before visiting someone at home. The statement above is(true/ false).
A. 对
B. 错
F-H实验中,用于消除热电子在阴极附近的堆积,以提高阴极热发射效率的是()
A. 灯丝电压
B. 第一加速栅极
C. 第二加速栅极
D. 拒斥电压
F-H实验中,阴极K被灯丝加热产生热电子,其发射热电子的多少可由()控制。
A. 灯丝电压
B. 第一加速栅极
C. 第二加速栅极
D. 拒斥电压