关于催产素静脉滴注，下列正确的是（）。 A.用于协调性子宫收缩乏力，以加强宫缩 B.

If you left your book on the table overnight, you would find the following morning that it was still exactly when you had left it, provided nobody had moved it. If a ball is made to roll on a very smooth surface, it will roll a long distance unless something stops it or changes its direction. This tendency of an object to remain at rest unless something moves it and to continue moving unless something stops it is known as the Law of Inertia.
The following examples show the truth of this law.

• (a) Put a table-cloth on a table and arrange a pile of books on it. Hold one edge of the tablecloth and pull it quickly. The table-cloth will come off, leaving the pile of books undisturbed.
• (b) Place a small piece of cardboard on an open jar and place a coin on it directly over its mouth. Use one finger to flick the piece of cardboard away. You will notice that the coin drops into the jar.
• (c) Sitting in a car which starts suddenly, you feel you are jerked backwards. In fact, you are not jerked backwards. Your lower half, which is in contact with the cushion, is forced to move forward with the car, and the upper part of your body, which remained at rest, is left behind.

In the first example, the pile of books on the table-cloth will ______.

A．be broken into pieces

B．scatter onto the ground

C．remain in its position of rest

D．be wrapped in the table-cloth

f（x）是定义在R上的函数，对x，y∈R都有f（x+y）=f（x）+f（y），且当x＞0时，f（x）＜0，f（-1）=2．

（1）求证：f（x）为奇函数；

（2）求证：f（x）是R上的减函数；

（3）求f（x）在[-2，4]上的最值．

　　月亮，从古到今都能引人们无限的遐思，为了让大家更多地了解与月亮有关的科学知识和文化现象，我们班决定开展一次有关月亮的综合性活动，请你积极参与。  

(1)请为这次活动拟定—个主题。（例：“月亮，一个永恒的话题”“与月亮相约”）       

主题：________________________________________________________；   

(2)如果让你来当这次活动的主持人，请你为这次活动写一段精彩的主持词。

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(3)请你给同学们提供两种获取有关月亮信息的方法。

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CDMA2000 1X空中接口协议中数据链路层包括那两个子层（）

A.TUP

B.MAC

C.LAC

D.ISUP

以下哪个选项是构成E-R图的基本要素（）

A.实体集

B.属性

C.联系

D.文件