韶山4改型电力机车箍踏面剥离长度不大于（）。 A.20mm B.30mm C.40m

伽利略对自由落体运动的研究，开创了研究自然规律的科学方法，这就是（　　）

A．对自然现象进行总结归纳的方法

B．用科学实验进行探究的方法

C．对自然现象进行总结归纳，并用实验进行验证的方法

D．抽象思维、数学推导和科学实验相结合的方法

要在D盘当前文件夹下建立一个名为InfoBase．dat的顺序文件，应使用的语句是（ ）。

A． Book

B． 2_Seek

C．123.58

D． Book-1

A pet is an animal that (21) in your house. Over half the families in North America own pets. The most popular (22) axe dogs, fish and birds. Rabbits, hamsters and turtles are also popular. (23) some unpopular animals such as frogs, mice and snakes are pets.

People first (24) to keep pets about 12,000 years ago. The first pet was a dog. The dog (25) not become a pet because people (26) it was cute. It (27) a pet because it was useful. People used the dog for many things. The dog warned people (28) danger so wild animals didn’t attack people. It also ate leftover food. Later, dogs helped people take care (29) cows and sheep on farms.

Cats did not (30) pets for a long time. When the Egyptians first (31) to grow grain, mice ate it. The Egyptians were (32) to tame cats.

Today, people keep many (33) of pets. Animals such as canaries, parrots, mice and hamsters live in cages. They need people to bring them food and water and to keep their cages clean. Other animals, such as dogs and cats, need food and water, but they (34) take care of themselves (35) . They are good pets for people because they don’t need much care.

33（）

A．sort

B．type

C．kinds

D．groups

什么是公共事业管理协调中的沟通？其主要内容是什么？