施工中发现影响施工的地下障碍物时，承包人应于( )以内以书面形式通知工程师。A．4

一货轮航行到M处，测得灯塔S在货轮的北偏东15°相距20里处，随后货轮按北偏西30°的方向航行，半小时后，又测得灯塔在货轮的北偏东60°处，则货轮的航行速度为         

国际服务业与第三产业的关系是（）

A．存在紧密联系

B．也存在区别

C．不存在联系

D．联系不大

E．没有区别

The fact that most Americans live in urban areas does not mean that they reside in the center of large cities. In fact, more Americans live in the suburbs of large metropolitan areas than in the cities themselves.
The Bureau of the Census regards any area with more than 2,500 people as an urban area, and does not consider boundaries of cities and suburbs.
According to the Bureau, the political boundaries are less significant than the social and economic relationships and the transportation and communication systems that integrate a locale. The term used by the Bureau for an integrated metropolis is an MSA, which stands for Metropolitan Statistical Area. In general, an MSA is any area that contains a city and its surrounding suburbs and has a total population of 50,000 or more.
At the present time, the Bureau reports more than 280 MSAs, which together account for 75 percent of the US population. In addition, the Bureau recognizes 18 megapolises, that is, continuous adjacent metropolitan areas. One of the most obvious megapolises includes a chain of hundreds of cities and suburbs across 10 states on the East Coast from Massachusetts to Virginia, including Boston, New York, and Washington, D.C. In the Eastern Corridor, as it is called, a population of 45 million inhabitants is concentrated. Another megapolis that is growing rapidly is the California coast from San Francisco through Los Angeles to San Diego.

Which of the following are NOT considered important in defining an urban area

A．Political boundaries.

B．Transportation networks.

C．Social relationships.

D．Economic systems.

阅读下面的材料，按要求回答问题。

　　光明中学举行辩论赛，正方的观点是“养成良好风气主要靠自律（自我约束）”；反方的观点是“养成良好风气主要靠他律（他人约束）”。辩论时，双方唇枪舌剑，反方突然这样发问：“孙悟空不就被套了个紧箍咒？可见养成良好风气主要靠他律。”作为正方，你将怎样得体有力地回击反方？

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下肢静脉曲张能否手术的关键是（）

A.曲张静脉病变程度

B.交通静脉瓣膜功能是否健全

C.深静脉是否通畅

D.小隐静脉是否受累

E.以上均不是