防毒面具的使用要求:作业人员在()的环境中进行作业时,使用防毒面具。
A.不明毒物
B.不明浓度
C.有毒有害
D.陌生
参考答案:C
around the famous museum, we were taken to visit the Theme Park about five kilometers out of the city.
A.Having shown
B.Being shown
C.To be shown
D.Having been shown
轧槽是什么?