对于一条趋势线而言，一旦被突破或击穿，它将失去任何意义。( )

阅读理解。

      American school life is different(和…不同)from Chinese. American students usually get to school at around 8:30 in the morning. School starts at 9:00. They put their school bags in their lockers(柜子)and only take one book, one notebook and one pen to each class. In class, American students can sit in their seats(座位)when they answer their teachers’ questions. They often ask lots of questions in class.

      At around 12:00 students have lunch. American students don’t go home for lunch. They have it at school. Most students like chicken, hot dogs or hamburgers. At 13:00 in the afternoon, they begin to have classes. Their classes are usually over at 15:00. Then they join in school clubs or play sports.

1. American School starts at ______ in the morning.

A. eight thirty            

B. nine o’clock    

C. nine thirty

2. American students usually ______ in class.

A. eat lots of chicken      

B. read lots of books      

C. ask lots of questions

3. American students often ______ at 15:30 on weekdays(工作日).

A. play sports      

B. have classes      

C. eat lunch

4. The best title(标题)of this passage is “______”.

A. American School Clubs

B. American School Life

C. American School Dinner

已知a＞0，b＞0，2a+b=16，则ab的最大值为（    ）。

某同学利用如图所示装置探究人体吸入的空气和呼出的气体有何不同．回答：

（1）在A处吹气，现象是______；

（2）在A吸气20秒，此时______（填“呼出气”或“空气”）从B端进入石灰水，结果石灰水中没有明显现象；再在B处吹气20秒，石灰水明显变浑浊．据此判断：在空气和呼出气中，二氧化碳的含量哪个大？

患者男性，45岁，以“因回吸鼻涕带血3个月，右耳听力下降10天”就诊。患者3个月前开始出现回吸鼻涕带血，多为陈旧性血液，无鼻塞、头痛、咳痰等表现，未诊治。近10天出现右耳听力、减退、伴耳鸣，无眩晕、耳痛、耳流脓等。临床检查见：右侧耳道通畅，右鼓膜完整、内陷，鼓室有积液；鼻腔未见异常，间接鼻咽镜检查见右侧咽隐窝处黏膜粗糙不平，稍隆起。右侧颈部触及肿大淋巴结，质硬，固定。根据以上表现，回答如下问题。

如出现单侧持续性头痛，则产生的原因可能是（）。

A.肿大淋巴结压迫颈内静脉导致回流障碍

B.神经血管反射性痛

C.鼻部局部炎性感染

D.三叉神经眼支的末梢在硬脑膜处受压

E.肿大淋巴结侵蚀颈椎骨质

F.颅底骨质破坏

下表显示英国在世界贸易中居于领先地位。直接导致这一地位确立的原因是

（单位：亿马克）

年份	世界贸易总额	英国	法国	德国	美国
1850年	145	33.8	15	21	12.8

A．新航路的开辟    B．三角贸易盛行  

C．资产阶级革命   D．工业革命完成