主动差动回路是为了提升：（）。A、活塞杆的推力；B、活塞杆的速度

有关下图描述不正确的是

A．距今已有近400年历史，它不仅是我国而且也是世界上现存最早，保存最完整的巨大石拱桥

B．“没有桥墩，只有一个拱形的大桥洞”，可以使水流畅通无阻

C．洞顶左右两边各有两个拱形的小桥洞，以备发大水时减轻水对桥身的压力

D．下面没有桥墩，节省石料，上面有小桥洞减轻了桥身的重量

以下对物理学发展史的说法正确的是(      )

A．卡文迪许利用扭秤实验测得了静电常量

B．法拉第为了形象的描述电场首次引入电场线的概念

C．开普勒在前人积累的数据上提出了万有引力定律

D．牛顿利用理想斜面实验推翻了亚里斯多德关于运动需要力来维持的观点

阅读理解

     San  Francisco is a spectacular city. It is famous for its steep hills, its earthquakes and the prison island of Alcatraz, but its most famous landmark is the Golden Gate Bridge. This is one of the most beautiful

bridges in the world. It has a simple, graceful shape, and is painted in an attractive orange.

     Work on the Golden Gate Bridge started in 1933 and continued for the next four years. The total cost of the bridge was US$35 million. At that time, its span of 1,200 meters made the Golden Gate Bridge the

longest suspension(悬浮) bridge in the world. The bridge is 2.7 kilometers long and, at the middle point,

70 meters above the water of San Francisco Bay. The main cables that hold the bridge are one meter in

diameter. The bridge can safely withstand(抵挡) winds of up to 160 kilometers an hour, and it can sway(摇摆) as much as 8 meters in strong winds.

     On Thursday, May 27, 1937, 200,000 people walked across the bridge to mark its opening. People

are still allowed to walk across: it takes about half an hour each way. It is worth the effort. As you cross,

you understand the engineering skill that went into the construction of the bridge. You also get wonderful

views of San Francisco and the Bay Area.

      The Golden Gate Bridge has been the scene of many events since it was completed. It was shaken by

the earthquake of 1989. Daredevil(喜欢冒险的) pilots have flown their planes under it. Sadly, too, some people have taken their own lives by jumping from the bridge. But throughout its history, the Golden Gate Bridge has been the symbol of San Francisco, like the Temple of Heaven symbolizes Beijing and the

Eiffel Tower symbolizes Paris

1. How many things make San Francisco famous?

A. Two (its history and its present).

B. Three (steep hills, earthquakes, the prison island of Alcatraz).

C. Four (Golden Gate Bridge, steep hills, earthquakes, the prison island of Alcatraz).

D. Five (the orange color of the bridge, the shape of the bridge, steep hills, earthquakes, the prison island

of Alcatraz).

2. The Golden Gate Bridge has been there for ______ years.

A. less than 70      

B. more than 70  

C. about 15  

D. about 50

3. What is TRUE about the bridge?

A. It was greatly damaged by the earthquake in 1989.

B. It can fight back strong winds of up to 180 kilometers an hour.

C. It has caused many deaths since its opening.

D. It is the symbol of the history of San Francisco.  

社会主义初级阶段基本路线的两个基本点是（）。

A.坚持四项基本原则、坚持改革开放

B.坚持改革开放、坚持自力更生

C.坚持四项基本原则、坚持自力更生

D.坚持自力更生、坚持艰苦创业

票据保证可以作成于票据或粘单上，也可以另行。签订保证合同或者保证条款。 ( )