下列操作正确的是 A．用试管加热时，试管内液体不得超过试管_爱下问搜题

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问题选择题

下列操作正确的是

A．用试管加热时，试管内液体不得超过试管容积的2/3

B．将烧杯直接放在铁圈上加热

C．向酒精灯里添加酒精，不得超过酒精灯容积的1/2

D．滴瓶上的滴管取过试液后，直接放回原瓶

答案

答案：D

加热试管时，试管内的液体不得超过试管容积的1/3，A答案错误；烧杯加热时不能直接放到铁圈上加热应垫加石棉网，B答案错误；向酒精灯里添加酒精，不得超过酒精灯容积的3/4

完形填空

Little Bit
"Meow, meow, meow," is what I heard as I walked. I went to the noise and found there was a
36  black and white cat under a piece of wood. I picked him up and   37  he must be freezing to death. I   38  home with the cat held in my jacket.
My new best friend, who soon became known as Little Bit, received his name because he was almost     39     when I held him in my hands. He stood about five inches tail. Little Bit' s small size had a great advantage -- he   40  perfectly in the pocket of my jacket, which made 41  him everywhere very easy. Any time I was home, he wouldn' t leave my   42  . He was always eager to play with me. When I fell asleep at night, he would always roll up around my head to keep me   43 .
Unfortunately, I grew up. My teenage life   44  my relationship with Little Bit. I lived at such a fast pace (节奏) that I stopped making time for him. My free time was spent with my   45      instead. I would come in the house on my phone and not   46  him at all. His meows became an annoyance to me, but it wasn' t his fault that he   47  his best friend back.
Time had caused a   48  to Little Bit. His body began shutting down and by the time I realized   49  was wrong with him, he had already lost his balance. He lay there and looked at me, and   50  this day I still remember the 51  look in his bright green eyes. I took him to the vet (兽医), but there was nothing he could do. The last time I   52  him he wasn' t the same tiny cat I had found ten years before. Little Bit filled my arms and he was put to sleep that day.
Little Bit' s 53  made me realize how much he meant to me. He was always there for me when I   54  him. I regret our last years together and I feel sorry for not always being there for him. I will always   55  the special memories we made.

问答题简答题

简述漏电保护器的工作原理？