普通使用条件下，区别（）振动和噪音的标准约为频率1000Hz以下属于振动问题。A、滑

Taking away a city’s rubbish is a big job. Every day trucks come into a city to collect it. Most rubbish is made up of things we can’t eat or use. If we kept these things, we would soon have a mountain of rubbish.

In some cities the rubbish is collected and taken outside of city to a dump. Often the city dump is placed where the ground is low or there is a big hole. The kitchen rubbish is broken into small pieces and sent into the sewage system. The sewage system takes away the used water from toilets, bathtubs and other places.

To keep mice and flies away, some earth is used to cover the newly dumped rubbish. Later, grass may be planted on the rubbish-filled land. Finally , a house or a school may be built there, and then you’d never know that this had once been an old rubbish dump.

In other cities the rubbish is burnt in special places. The fire burns everything but the metal. Sometimes the metal can be used again in factories where things are made of metal. The food parts of rubbish are put in special piles where they slowly change into something called humus, which looks like black earth. It is rich with kinds of things that feed plants and help make them grow.

小题1:The underline word “sewage” in the passage means_______

A．排污

B．染色

C．洗涤

D．洗尘小题2:How can we keep the mice and flies away?

A．Some water is used to cover the rubbish.

B．Some earth can be used to cover the rubbish.

C．The fire burns the rubbish.

D．The sewage system takes away the rubbish.小题3:According to the passage, the food parts of rubbish can be used again_______.

A．to feed animals

B．to feed plants

C．to build a house

D．to make machines小题4:How should we take care of a used metal box according to the passage?

A．By burning it off

B．By putting it in water

C．By throwing it away

D．By reusing and recycling it.小题5:The main idea of the passage is ______

A to let us know taking away rubbish is a big job.

B. to explain the need for rubbish collection

C. to introduce different ways to treat rubbish

D. to tell people to take useful things out of rubbish

上自习课时，调皮的小明在教室走廊放声歌唱，他手摸喉头，感觉到喉头在________； 教室里的同学都听到了歌声，表明声音可以通过__________传播；正在静心思考的小娟 忙用手捂住耳朵，她认为小明的歌声是__________（填“乐音”或“噪声”）。

在教学中，通过学生观察所学事物或教师语言的形象描述，引导学生形成所学事物、过程的清晰表象，丰富他们的感性认识，从而使他们能够正确理解书本知识和发展认识能力的是( )。

A．直观性原则

B．启发性原则

C．循序渐进原则

D．巩固性原则

下列典故中发生了化学变化的是 [ ]

A．司马光砸缸

B．火烧赤壁

C．铁杵磨成针

D．凿壁偷光

高分辨率扫描通常用于

A．肺弥漫性、间质性病变

B．肾上腺

C．视神经

D．内耳

E．肺结节性病变