安装(回撤)起重作业管理中规定新购或维修的所有起吊机具均经检验,并有()。
A.生产资格证
B.防护等级证
C.防爆合格证
D.出厂合格证
参考答案:D
There is ______ wrong with this computer. It doesn't work well. [ ]
A. something
B. anything
C. everything
D. nothing
铅玻璃的密度为3.74g/cm3,与()密度接近。
A.合成金红石
B.合成尖晶石
C.立方氧化锆
D.钛酸锶