零件图上符号的含义表示零件的精度要求之一，如：“↗”表示台阶轴对（）。 A.轴线的圆

一棵二叉树第六层(根结点为第一层)的结点数最多为 【4】 个。

导致患者双下肢弛缓性瘫痪的直接原因可能是

A．脑栓塞

B．血钾异常

C．重症肌无力

D．呼吸性碱中毒

When Dave was eighteen, he bought a secondhand car for 200 so that he could travel to and from work more (1) than by bus. It worked quite well for a few years, but then it got so old, and it was costing him (2) much in repairs that he decided that he had better (3) it.

He asked among his friends to see if anyone was particularly (4) to buy a cheap car, but they all knew that it was falling to pieces, so (5) of them had any desire to buy it. Dave’s friend Sam saw that he was (6) when they met one evening, and said, "What’s (7) , Dave"

Dave told him, and Sam answered, "Well, what about advertising it in the paper You may (8) more for it that way than the cost of the advertisement!" Thinking that Sam’s (9) was sensible, he put an advertisement in an evening paper, which read "For sale: small car, (10) very little petrol, only two owners. Bargain at 50. " For two days after the advertisement first appeared, there was no (11) . But then on Saturday evening he had an enquiry. A man rang up and said he would like to (12) him about the car. "All right, " Dave said, feeling happy. He asked the man whether ten o’clock the next morning would be (13) or not. "Fine, " the man said, "and I’ll (14) my wife. We intend to go for a ride in it to (15) it. "

The next morning, at a quarter to ten, Dave parked the car in the square outside his front door, (16) to wait there for the people who had (17) his advertisement. Even Dave had to (18) that the car really looked like a wreck. Then, soon after he had got the car as clean (19) it could be, a police car stopped just behind him and a policeman got out. He looked at Dave’s car and then said, "Have you reported this (20) to us yet, sir\

8().

A.learn 

B.miss 

C.get 

D.find

“乡镇整洁工程”的具体内容是什么？

200×年×月×日15时，位于某县各子乡宋城村北700m，某井下作业公司试油三大队作业20队，对某井进行射孔作业后，发生井喷，大量含硫化氢的气体喷出，造成村民6人死亡(在l0多万人的紧急疏散过程中，因年老体弱、惊吓、颠簸、中风、交通事故等原因还死亡15人)，24人中等中毒，440余人轻度中毒，轻质油污染庄稼近700亩，中毒死亡大牲畜7头，直接经济损失约60万元的井喷事故。
某井是一口预探井，完钻井深3282.8m，人工井底3032m，钻探目的层是新生界孔店组二段。事发当日15时，由某井下作业公司物理站射孔一队用90型射孔枪对该油层进行射孔。15时10分引爆射孔弹，投射子弹77颗，射发率100%。在开始上提电缆时，井口发生外溢，而且外溢量逐渐增大，溢出的水中有气泡。当电缆全部从井中提出后，作业20队副队长李某立即带领当班的5名作业工人抢装事先备好的总闸门，穿上了总闸门的8条大螺栓并拧紧了对角的4条，关闭了总闸门。在准备关闭套管闸门时，因有硫化氢气体随同压井液、轻质油及天然气一同喷出，强烈的气流使人无法接近套管闸门，当班工人不得不从井口撤离。撤离现场后，副队长李某立即派人电话报告上级，同时通知附近两个砖窑灭火，并到距井场最近的宋城村，广播发生井喷的消息，通知村民转移。
得到某井井喷的消息后，石油管理局、市公安局、当地驻军、当地县委，县政府，都组织了抢险人员赶赴现场。
经调查，并对该井地质、钻井、测井、试油、射孔等有关技术资料和原始记录进行反复分析，这次事故的主要原因是：钻井、录井、测井资料都没有发生硫化氢，造成了对该射孔层地下情况缺乏全面准确详尽的认识，把这一层作为新层和油水同层进行常规试油，对所试层段中含硫化氢没有准备。因此，此次事故属于不可预见的性质。
在调查中还发现，某井下作业公司20队存在执行制度不严的问题，没有严格按照设计要求组织施工，用总闸门代替防喷阀门等现象。
根据以上情形回答下列问题，1～2题为单选题，只有一个正确的答案，3～8题为多选题，有两个或两个以上的正确答案。

应急演习根据演习的基本内容不同可以分为( )。

A．基础训练

B．专业训练

C．体能训练

D．战术训练

E．自选科目训练