离心技术分为（） A.普通离心法 B.差速离心法 C.密度梯度离心法 D.分析性超速

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.

The Law of Inertia is a law concerning ______.

A．motion

B．distance

C．position

D．direction

已知：（a+b）⁰=1，则a与b的关系：（    ）。

依照例句，再写出两个你对“语文”理解的比喻句。

例句：语文是滋味甘醇的美酒，让人回味无穷。

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女方患有白化病，欲与无血缘关系表型正常的男性婚配

此疾病属于（）

A.遗传性疾病

B.先天性疾病

C.家族性疾病

D.多基因病

E.染色体病

特殊情况下，需要（）时，由各供电局负责生产的总工或副局长批准执行。

A.改变设备的试验方法

B.延长试验周期

C.增删试验项目

D.降低试验标准