霍乱病人（）。 A.大便为水样便 B.黏液脓血便 C.不消化样大便 D.米泔水样便

与原点距离为3个单位长度的点有______个，它们分别表示有理数______和______．

如图所示，在真空室中有一水平放置的不带电平行板电容器，板间距离为d，电容为C，上板B接地．现有大量质量均为m、带电量均为q的小油滴，以相同的初速度持续不断地从两板正中间沿图中虚线所示方向射入，第一滴油滴正好落到下板A的正中央P点．如果能落到A板的油滴仅有N滴，且第N+l滴油滴刚好能飞离电场，假定落到A板的油滴的电量能被板全部吸收，不考虑油滴间的相互作用，重力加速度为g，则下列说法错误的是（　　）

A．第1滴油和第N+1滴油滴运动时间之比为1：2

B．落到A板的油滴数N=

C．第N+1滴油滴通过电场的整个过程所增加的动能等于

D．第N+1滴油滴通过电场的整个过程所减少的机械能等于

Mail was usually carried west on ships that sailed around the bottom of South America and then north to California．That could take several months.  

So, in eighteen fifty-seven, D.C．Lawmakers in Congress（国会） in Washington wanted to make it possible to send mail all the way across the United States by land．Congress offered to help any company that would try to deliver mail overland to the West Coast. A man named John Butterfield accepted this offer. He developed plans for a company that would carry the mail—and passengers, too.

Congress gave John Butterfield six hundred thousand dollars to start his company. In return, he had to promise that the mail would travel from Saint Louis, Missouri, to San Francisco, California, in twenty-five days or less.

It was not possible to travel straight through because of the Rocky Mountains and the deep snow that fell in winter. So the stagecoach（马车） would travel south from Saint Louis to El Paso, Texas, then over to southern California, then north to San Francisco. The distance was about four thousand five hundred kilometers.

Two hundred of these stations were built, each about thirty-two kilometers apart. The workers were to quickly change the horses or mules whenever a stagecoach reached the station. There could be no delay. Each stagecoach was to travel nearly two hundred kilometers a day.

One hundred stagecoaches were built and painted red or dark green. They were the most modern coaches that money could buy. They were designed to hold as many as nine passengers and twelve thousand pieces of mail. The seats inside could be folded down to make beds. Passengers either slept on them or on the bags of mail.

The cost would be one hundred fifty dollars to travel from Saint Louis to San Francisco. If a passenger was not going all the way, the cost was about ten cents a kilometer. The passengers had to buy their own food at the stations. The stagecoach would stop for forty minutes, two times a day.

The company warned passengers about the possible dangers. A poster said: “You will be traveling through Indian country and the safety of your person cannot by granted by anyone but God.”

1．What is the passage mainly about?

A．Different ways of sending mail in the United States.

B．The difficulty in sending mails across the USA by land.

C．The first stagecoaches that carried both passengers and mail.

D．The history of the first stagecoaches carrying mail to the American West.

2．The reason why Lawmakers wanted to send mail by land was that ________.

A．mail was usually carried west on ships  

B．it was safer to travel to send mail by land

C．it would take less time to send mail by land

D．stagecoaches could carry passengers and mail

3．As is described in the passage, the stagecoach ________.

A．could only stop once a day           

B．was modern with seats ,beds and cooking equipment

C．was a closed wagon operated only by skillful drivers.

D．had different horses or mules pulled all the way

4．What can we learn from the passage?

A．John Buttterfield got thousands of dollars for delivering mail in stagecoaches.

B．John Buttterfield kept his promise to deliver mail straight to the West Coast.

C．Passengers might be robbed by Indians when traveling through the West.

D．Passengers needed to pay one hundred dollars for their journey. 

对具有n个元素的有序表采用二分查找，则算法的时间复杂性为______。

A．O(n)

B．O(n²)

C．O(1)

D．O(log₂n)

妇科常用相应的物理学诊断检查有

A．超声检查、X线检查、内镜检查等
B．盆腔检查
C．双合诊和 * * 窥器检查
D．膀胱截石位
E．采集病史、进行体格检查、制订相应的护理计划并实施。