二尖瓣关闭不全不可能出现的体征是（） A.肺动脉瓣区第二心音亢进 B.杂音常在3级以

阅读理解。

    One Sunday morning, I decided to buy a computer to use forschool. I went to the biggest store in town, which sold all kinds of computers. There were so many computers there that I didn't know how to choose a right one.

    "Hi! What  can I do  for you?" A young  man  greeted  me with a sweet  smile. He looked  like  not  a

salesman but a student like me. I sensed a strange feeling -- as if I had met him before. He began patiently showing me each model. With his help, I decided to buy one computer with enough functions at a very low price. I enjoyed this shopping experience because of his smile. A few months later, something was  wrong with my computer. I went back to the store to have it fixed. When I arrived there, what I saw was  still his

smile. As soon as I told  him my problem, he comforted  me  immediately and t ried his best to  solve  the

problem for me. I was quite grateful for his sweet smile and good service.

    When I went back to school, his smile often appeared in my mind. I don't  know  whether  we'll  meet

each other again, but his sweet smile will stay there in my  memory and  deep  in my  heart.  Smiling  is  the

most peaceful language in the daily life.

1. After reading the story, we can know that the writer is a __________.

A. student

B. salesman

C. doctor

D. reporter

2. According to the passage, why was the writer grateful to this salesman?

A. Because the salesman recommended the cheapest computer.

B. Because the salesman gave the writer his sweet smile and good service.

C. Because the salesman recommended the computer with enough functions.

D. Because the salesman showed how to use the computer correctly.

3. What does the writer mainly want to tell us in the story?

A. The way to choose a right computer.

B. The way to use a computer correctly.

C. The importance of smiling in the daily life.

D. The importance of computers in the daily life

某企业为小型货车生产厂，地处我国华北地区，年产小型货车5万辆，现有职工1100余人。
厂区主要建筑物有冲压车间、装焊车间、涂装车间、扳金车间、装配车间、外协配套库、半成品库和办公楼。
冲压车间设有三条冲压生产线。库房和车间使用6台5t单梁桥式起重机吊装原材料，装配生产线上设置多台地面操作式单梁电动葫芦和多台小吨位的平衡式起重机，在汽车板材冲压生产线上设置4台大吨位桥式起重机。
车身涂装工艺采用三涂层三烘干的涂装工艺，涂装运输采用自动化运输方式。漆前表面处理和电泳采用悬挂运输方式，中层涂层和面漆涂装线采用地面运输方式。生产线设中央控制室监控设备运行状况。喷漆室采用上送风、下排风的通风方式。喷漆室外附设有调漆室。
整车总装配采用强制流水装配线。
车身装焊线焊机选用悬挂电焊机、固定焊机、二氧化碳气体保护焊机等。车身装焊工艺主要设备包括各类焊机、夹具、检具、车身总成调整线和输送设备。
车架装焊采用胎具集中装配原则，组合件和小型部件预先装焊好与其他零件一起进入总装胎具焊接线。焊接方法采用二氧化碳气体保护焊。装焊设备主要包括焊机、总成焊接胎具、部件焊接胎具、小件焊接胎具以及输送系统设备等。
装焊车间通风系统良好。
该企业采用无轨运输，全厂原材料、配套件、成品和燃料等的运输采用汽车运输，厂内半成品运输以叉车为主。全厂现有小客车8辆，货车16辆，叉车15辆。厂区道路采用环形布局，主干道宽度8m、转弯半径大于9m，次干道宽度5m、转弯半径大于6m，厂区内主要道路两侧进行了绿化，种植有草坪、灌木、松树和杨树。
该企业主要公用和辅助设施有变配电站、锅炉房和空压站。变配电站电压等级为35kV，内设5台变压器，总安装容量为3900kVA，厂区高、低压供电系统均采用电缆放射式直埋或电缆沟敷设，厂区道路设路灯照明。锅炉房内设3台4t/h燃煤锅炉，为厂区生产和生活提供蒸汽。空压站安装有4台供气量为20m³/min的空气压缩机，为全厂生产提供压缩空气。
某日，冲压车间进行起重机吊装板材作业，工人甲、乙挂上吊钩后，示意天车司机开始起吊。随着板材徐徐升起，工人甲发现板材倾斜，与工人乙商议是否需要停车调整，工人乙说：“不必停车，我扶着就行”。作业场所地面物品摆放杂乱，工人乙手扶板材侧身而行，被脚下物品绊倒，板材随之倾斜、脱钩砸在工人乙身上，造成工人乙死亡。
根据以上场景，回答下列问题：

颅内压升高不能出现（）

A.头痛

B.恶心

C.视觉障碍

D.脑疝

E.呕吐

最符合风湿性疾病特点的是()

A．多系统多器官性病变

B．心血管病变

C．血管壁病变

D．肾脏损害

E．皮肤及关节病变

民用黑火药的一般配比是硝酸钾：硫磺：木炭=（）。

A.65：20：16

B.75：10：15

C.70：15：15

D.80：10：10