问题 阅读理解

阅读短文,选择正确答案。

March 12th,

Dear Diary,

      Today was Tree-planting Day. It was also a good day for me. I was very happy. At about 6 o'clock, I

got up and put on my clothes. At 6: 30, I had bread and milk for breakfast. Then I went to school. The teacher

took us to a hill. He taught us to plant trees there. We liked to do this, so all of us planted trees happily. We

planted about one hundred trees this morning. We watered them. We hoped they can grow up quickly. At 1: 00

in the afternoon, I got home. My clothes were dirty, but I was happy.

                                        John

1. When is Tree-planting Day?

A. March 12th.

B. March 8th.

C. March 9th.

2. What did John do today? 

A. He growed flowers.

B. He planted trees.

C. He washed clothes.

3. How did John feel?

A. He felt happy.

B. He felt angry.

C. He felt sad.

答案

1. A  2. B  3. A

问答题

背景资料


某高层办公楼,总建筑面积137500m2,地下3层,地上25层。业主与施工总承包单位签订了施工总承包合同,并委托了工程监理单位。
施工总承包单位完成桩基工程后,将深基坑支护工程的设计委托给了专业设计单位,并自行决定将基坑支护和土方开挖工程分包给了一家专业分包单位施工。专业设计单位根据业主提供的勘察报告完成了基坑支护设计后,即将设计文件直接给了专业分包单位。专业分包单位在收到设计文件后编制了基坑支护工程和降水工程专项施工组织方案,方案经施工总承包单位项目经理签字后即由专业分包单位组织了施工,专业分包单位在开工前进行了三级安全教育。
专业分包单位在施工过程中,由负责质量管理工作的施工人员兼管现场安全生产监督工作,土方开挖到接近基坑设计标高(自然地坪下8.5m)时,总监理工程师发现基坑四周地表出现裂缝,即向施工总承包单位发出书面通知,要求停止施工并要求立即撤离现场,施工人员查明原因后再恢复施工。但总承包单位认为地表裂缝属正常现象,没有予以理睬。不久基坑发生了严重坍塌,并造成4名施工人员被掩埋,经抢救3人死亡、1人重伤。事故发生后,专业分包单位立即向有关安全生产监督管理部门上报了事故情况。经事故调查组调查,造成坍塌事故的主要原因,是由于地质勘察资料中未表明地下存在古河道,基坑支护设计中未能考虑这一因素而造成的。事故造成直接经济损失80万元,于是专业分包单位要求设计单位赔偿事故损失80万元。

问题


本起事故可定为哪种等级的事故请说明理由。

单项选择题