在关系数据库的关系模型中，采用 (21) 表达实体集以及实体集之间的联系。关系数据库

阅读短文，判断下面的句子是否与短文内容相符，相符的在括号里画“√”，不相符的画“×”。

      Do you know the differences between rabbits and hares? Rabbits look like hares. Both of them have long

ears and short tails. And both of them eat plants. But hares are usually bigger than rabbits. They have longer ears

and legs. 

      Rabbits are popular pets. They are gentle and friendly animals. When baby rabbits are born, they can't see

anything at first and they have no hair. Eight days later their eyes open and they begin to grow some hair.

      Hares can weigh 5 kilos. They can run very fast and jump high. It can run about 50 kilometres in an hour.

Baby hares open their eyes and they are very active soon after they are born.

( ) 1. Hares and rabbits are the same. 

( ) 2. Both hares' and rabbits' ears are long.

( ) 3. Rabbits are usually bigger than hares.

( ) 4. Hares' ears are longer than rabbits'.

( ) 5. Baby hares open their eyes earlier than baby rabbits.

危险废物贮存是指危险废物再利用或无害化处理和最终处置前的存放行为。根据《国务院关于全国危险废物和医疗废物处置设施建设规划的批复》，到2006年，在全国各省及部分市、地区将建成30多个危险废物集中处置中心和300多个医疗废物集中处置中心。这些集中处置中心都附设了集中贮存设施。某地建设一危险废物集中处置中心，处置中心附设了集中贮存设施，贮存设施周边有一居民区和一地表水域，贮存设施基础防渗层为2m厚黏土层。贮存设施选址地质结构稳定，地震裂度不超过7度的区域。
根据以上内容，回答以下问题。

计算题：某班组当月生产合格钢锭995t，跑漏损失2.2t，钢锭减少0.5t，下车间返回废品2.3t，问该班组本月钢锭合格率是多少？

紧急状态处置，是指公安机关为维护国家安全和社会治安秩序，对突发的重大暴力犯罪，重大治安事件和重大治安灾害事故依法采取的非常措施。( )

活性污泥培养成熟后，就要开始试运行，其目的是（）。