水利水电施工企业应按规定进行施工安全、自然灾害等危险源辨识、评价，确定危险等级。
AutoCAD绘图时的线型，下列正确的说法有（）。 ["可以调入各种线型","只能使用层中定义的线型","线型可以在需要的时候随意改变","可以使用系统定义的任何线型"]
下述关于商品条码的使用规定正确的有（） ["企业必须具有合法的营业执照","企业必须具有卫生许可证","到当地物品编码管理机构申请注册","并经当地物品编码管理机构审核"]
什么是能源？什么是“能源问题”？“能源问题”的实质是什么？
An indirect radar echo is caused by a reflection of the main lobe of the radar beam off the observer’s vessel. Which of the following is NOT a characteristic of indirect echoes? （） ["Their bearing is almost constant，even when the true bearing of the contact changes appreciably","They always appear on a bearing of 90°From the true bearing of the contact","The indirect echoes usually appear in shadow sectors","When plotted，their movements are usually abnormal"]
什么是单品牌上柜率？
