在喹诺酮类抗菌药的构效关系中，必要的基团是（）。 A.8位哌嗪基 B.1位乙基取代

选择性β₁受体阻断药有（）

A.美托洛尔

B.阿替洛尔

C.普萘洛尔

D.醋丁洛尔

E.吲哚洛尔

Jiuzhaigou is a very beautiful place. It is in the Aba Tibetan and Qiang Autonomous Region in Sichuan Province. Jiuzhaigou is a valley. It is more than 40 kilometers long. The green and golden trees, the lofty and multi-shaped mountains and the clear and colorful waters form the unique beauty of Jiuzhaogou. The water of Jiuzhaigou is the soul of the beauty. There are more than 100 lakes of different shapes in the valley. These lakes have wonderful colors. They are called “haizi”, which means son of the sea. It is these beautiful lakes that make Jiuzhaigou a fantastic place. Between the forests and the lakes, there are nine Tibetan villages. The name Jiuzhaigou means Nine Village Valley.

Jiuzhaigou was discovered because of a panda rescue program. The pandas were once endangered because the bamboo there was blooming. When people came to rescue the pandas, they were surprised by the beauty of Jiuzhaigou. After that, Jiuzhaigou became a protected scenic area.

In China, there is a saying which goes like this: No mountain is worth seeing after you have seen Mount Huang and no other body of water will attract you after you have visited Jiuzhaigou. The beauty of Jiuzhaigou cannot be described with mere words. The best way to enjoy this fairyland is to go there. See you in Jiuzhaigou.

小题1: What is the best title for the passage? （no more than 3 words）

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小题2: How long is the Jiuzhaigou Valley? （no more than 7 words）

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小题3: How was the Jiuzhaigou Valley discovered? （no more than 9 words）

小题4: What does the name Jiuzhaigou mean? （no more than 7 words）

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Tr30×6表示()螺纹，旋向为()螺纹，螺距为()mm。

A．矩形， 右， 12

B．三角， 右， 6

C．梯形， 左， 6

D．梯形， 右， 6

省级以上人民政府对实现水污染达标排放仍不能达到国家规定有污染量削减任务的企业实施( )。

A．限期治理制度
B．排污收费制度
C．超标罚款制度
D．重点污染物排放量的核定制度

塔式起重机基础设计时，基础的混凝土强度应当（），并有试压块试验报告。

A、≥C25

B、≥C30

C、≥C40

D、≥C35