题目

In my driving lesson, a traffic rule that impressed me most is that in no time ________ when the traffic lights turn red. A . all vehicles should stop B . should all vehicles stop C . should stop all vehicles D . stop all vehicles 答案：A在制作洋葱表皮细胞装片时，正确的方法是（ ）A．应选用薄而透明的外表皮 B．应选用较厚的内表皮C．应选用薄而透明的内表皮 D．先滴碘液，再放洋葱表皮