二级动火作业指在石油库、加油站重点区域的动火作业。
参考答案：错
解析：二级动火作业指在石油库、加油站火灾危险区域的动火作业。
句型转换（每空一词）。
1. I read English books once a week.（改为一般疑问句）
you English books once a week?
2. She often eats fruit and vegetables.（对画线部分提问）
does she fruit and vegetables?
3. He sometimes goes skateboarding with his friends.（对画线部分提问）
does he sometimes with his friends?
4. He went to the mountains last weekend.（用sometimes代替last weekend并改写句子）
He sometimes to the mountains.
5. Jean often has milk for breakfast. (用now代替often并改写句子）
Jean milk for breakfast now.
某公司承揽了某球罐的安装任务，球罐为300m3。球罐在充水防水过程中对基础的沉降进行了观测，坐了实测记录；项目部门进行了焊接工艺评定试验，并按照相关的条例取得了有关开工许可。安装方法采用倒装法，对容器进行了检验和试验。
有关沉降观测正确的是( )。
A．充水前
B．充水到球壳内直径的1/2
C．放水前
D．充满水48小时后
