动会聚的原因是由于红、蓝光栅与绿光栅大小不一致而产生的会聚调整要求,它一般调整光栅的()位置。
A、整屏
B、屏幕上下边
C、屏幕边沿
D、屏幕中心
参考答案:C
—Could you please tell Lucy that I want to talk to her?
—Sure, I will let her know as soon as she _______ back..
A.came
B.will come
C.come
D.comes
用于防止介质倒流的阀门是()。
A.关断阀
B.止回阀
C.调节阀
D.阻隔阀