关于抽样误差，正确的是 A．样本统计量与总体参数之间的差别 B．由于抽样产生的各观察

“青出于蓝而胜于蓝，冰水为之而寒于水”所反映出师生关系应具备的特点是( )。

A．尊师爱生
B．教学相长
C．民主平等
D．密切融洽

下列划线成语使用正确的一项是[ ]

A．王东张皇失措地跑到学校，累得上气不接下气。

B．一些沿海城市飞速发展，现在的景象日新月异，和内地相比真可谓世外桃源。

C．这一点火焰将永远燃着，正像一个母亲的眼泪，正像一个儿子的英勇，那样永垂不朽。

D．既然敌我力量悬殊，与其负隅顽抗，全军覆没，不如撤退，以保全有生力量。

对乙肝病毒感染具有保护作用的是（）

A.抗-HBe

B.抗-HBs

C.DNA聚合酶

D.抗核抗体

E.抗-HBC

化学是一门以实验为基础的自然科学。依据实验目的设计切实可行的的实验方     案是科学探究中的重要环节。   

（1）用甲装置测定水的组成。a试管中气体能燃烧，该气体是_________，正极与负极产生气体的质量比为_____。甲装置中发生反应的化学方程式为__________________。   

（2）小红同学用乙装置进行探究实验，观察现象得出结论。   

①蜡烛中含有氢元素，她依据的现象是 ______________________ 。  

②一段时间后，小红观察到蜡烛熄灭，由此得出可燃物燃烧必须具备的条件是_________。   

（3）用丙装置测定空气中氧气的含量。下列有关 该实验的说法中，正确的是_______（填字母序号）。  

A. 实验时红磷一定要足量      

B. 点燃红磷前先用弹簧夹夹紧乳胶管  

C. 红磷熄灭后立刻打开弹簧夹  

D. 最终进入瓶中水的体积约为消耗氧气的体积

For many people today, reading is no longer relaxation. To keep up their work they must read letters, reports, trade publications, interoffice communications, not to mention newspapers and magazines: a never ending flood of words. In (1) a job or advancing in one, the ability to read and comprehend (2) can mean the difference between success and failure. Yet the unfortunate fact is that most of us are (3) readers. Most of us develop poor reading (4) at an early age, and never get over them. The main deficiency (5) in the actual stuff of language itself—words. Taken individually, words have (6) meaning until they are strung together into phrases, sentences and paragraphs. (7) , however, the untrained reader does not read groups of words. He laboriously reads one word at a time, often regressing to (8) words or passages. Regression, the tendency to look back over (9) you have just read, is a common bad habit in reading. Another habit which (10) down the speed of reading is vocalization—sounding each word either orally or mentally as (11) reads.
To overcome these bad habits, some reading clinics use a device called an (12) , which moves a bar(or curtain) down the page at a predetermined speed. The bar is set at a slightly faster rate (13) the reader finds comfortable, in order to "stretch" him. The accelerator forces the reader to read fast, (14) word by word reading, regression and subvocalization practically impossible. At first (15) is sacrificed for speed. But when you learn to read ideas and concepts, you will not only read faster, (16) your comprehension will improve. Many people have found (17) reading skill drastically improved after some training. (18) Charlie Au, a business manager, for instance. His reading rate was a reasonably good 172words a minute (19) the training; now it is an excellent 1,378 words a minute. He is delighted that how he can (20) a lot more reading material in a short period of time.

A．but
B．nor
C．or
D．for