进行碳弧气刨操作时电弧切割时噪声较大,操作者应戴()。
参考答案:耳塞
Sally used to be ______, but now she enjoys meeting and talking to new friends.
A. shy B. active C. outgoing
小李同学用托盘天平测量物体的质量,操作情况如图所示,其中错误的操作有:
(1)_________________________________;
(2)_________________________________;
(3)_________________________________。