题目

Tom and his parents ________at 10:00 last night. A.      was sleeping  B. were sleeping   C. are sleeping        D. is sleeping 答案：B有关平板划线法操作正确的是（　 ） 　 A．使用已灭菌的接种环、培养皿，操作过程中不再灭菌 　 B．打开含菌种的试管需通过火焰灭菌，取出菌种后需马上塞上棉塞 　 C．将沾有菌种的接种环迅速伸入平板内，划三至五条平行线即可 　 D．最后将平板倒置，放入培养箱中培养