前后的镜片组固定座采用压铸铝，喷漆为黑色或者白色。
The front and back cells are cast-aluminum painted white, or black.
在大型会议上，视觉辅助是有用的，它最好是黑色或者白色背景。
Visual AIDS are useful in large meetings and should only be done with black type on white background.
纸板(最好是黑色或者白色的，别的颜色也可以)，棉花，胶水，剪刀和笔。
Card stock (white or black is ideal, but any colour is fine), cotton wool, glue, scissors and a pen.
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