已知随机变量ξ～B（20，p），则Dξ的最大值为______．

称取三份锌粉，分别盛于甲、乙、丙三支试管中 。甲加入50mLpH=3的盐酸，乙加入50mLpH=3的醋酸，丙加入50mLpH=3的醋酸及少量的胆矾粉末。若反应终了，生成氢气的体积一样多，且没有剩余的锌，则下列说法错误的是 [ ]

A．开始时反应速率的大小：甲=乙=丙          

B．反应过程中，甲、乙速率相同

C．反应终了时，所需时间的大小：甲>乙>丙

D．三支试管中参加反应的锌的质量：甲=乙<丙 

根据下面的材料，回答问题。

　　现在私家车越来越多，车尾的个性标语也形形色色。如，挑衅型：“你快你飞过去”；搞笑型：“不要迷恋姐，姐开的是块铁”、“你就当我是红灯”；恐吓型：“至尊新手，擅长急刹，随时熄火”、“驾校除名，自学成才”；正话反说型：“告诉你个秘密，我喝酒了”。这些标语和与之相配的滑稽、俏皮的卡通图像，引来了众多车主的跟风。有人将其称为“车尾文化”。

　　人们对此褒贬不一。请你就此“车尾文化”发表自己的观点，要求观点明确，字数不超过45字。

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阅读理解。

     Most people, when they travel to space, would like to stay in

orbit for a few days or more. And this stands to reason, if you're

paying $ 20,000 for your trip to orbit!  So in order for tourism to

reach its full potential there's going to be a need for orbital

accommodation-or space hotels. What would a space hotel

actually be like to visit? Hotels in orbit will offer the services you

expect from a hotel-private rooms, meals, bars. But they'll also

offer two unique experiences: impressive views-of Earth and

space~ and the endless entertainment of living in zero gravity-

including sports and other activities that make use of this.

   The hotels themselves will vary greatly-from being quite

simple in the early days to huge luxury structures at a later date.

It's actually surprising that as later as 1997,very few designs for

space hotels were published. This is mainly because those who

might be expected to design them haven't expected lauch costs to

come down far enough to make them possible.

     Lots of people who've been to space have described vividly

what it's like to live in zero gravity. There are obviously all sorts of

possibilities for dancing, gymnastics, and zero-G sports. Luckily,

you don't need to sleep much living in zero gravity, so you'll have

plenty of time for relaxing by hanging out in a bar with a window

looking down at the turning Earth below.

      Of course all good things have come to an end, unfortunately.

And so after a few days you'll find yourself heading back though

you'll be much more expert at exercising in zero gravity than you

were when you arrived. You'll be thinking how soon you can save

up enough to get back up again-or maybe you should change jobs

to get to work in an orbiting hotel!

1. When traveling in space, most people would like to stay in orbit for a few days because ____.      

A. it is expensive to travel in space

B. they would find the possible life in other star systems

C. they could enjoy the luxury of space hotels

D. they want to realise the full potential of tourism

2. Which of the following is a unique experience that space hotels will offer? 

A. The gravitational pull.  

B. The special views.

C. The relaxation in a bar. 

D. The space walk.

3. Which of the following is NOT discussed in the passage?   

A. When was the space traveling made possible?

B. What are the unique experiences that space hotels will offer?

C. Why were there not many published designs for space hotels?

D. How can the travelers enjoy themselves in space hotels?

4. This passage is mainly about ____. 

A. traveling in space

B. the ways of living in space hotels

C. zero gravity and space hotels

D. the description of space hotels

档案工作的服务方向是档案工作（）的集中表现。

在氨合成反应中，提高平衡氨含量的措施有（）。

A.降低温度、降低压力

B.提高温度、提高压力

C.降低温度、提高压力

D.增加惰气含量