问题 单项选择题

()是指:接收天线增益与噪声温度的比值。

A.G/T

B.D/T

C.DAB

D.HEO

答案

参考答案:A

问答题

阅读下列材料,回答问题: 光污染及防治 光污染是指因光辐射过量而对生活、生产环境以及人体健康产生的不良影响. 最常见的光污染是眩光.都市中的宾馆、饭店、写字楼等地方常用玻璃、铝合金材料装饰其外墙.这些材料能强烈的反射太阳光,使人宛如生活在镜子世界之中.另外,夜晚迎面驶来的汽车灯光,电焊、熔炉发出的强光,专用仪器设备产生的红外线、紫外线等均会造成严重的光污染. 光污染的危害是:

①导致人的视力下降,白内障发病率增高;

②“人工白昼污染”会使人的生物节律受到破坏,产生失眠、神经衰弱等各种不适症,致使精力不振;

③现代舞厅中的“彩光”污染使人眼花缭乱,发生头昏、头疼、精神紧张等症状.如果人体长期受到这些光源中紫外线的照射,还会诱发白血病等.

(1)以下常见的几种职业,不易受到光污染危害的是         

A. 炼钢工人

B.纺织工人

C.出租车司机

D.电焊工人

(2)下列的四个娱乐场所中,易受到光污染危害的是            

A.现代舞厅  

B.电影院  

C.剧场    

D.音乐厅

(3)请你就如何有效地预防光污染,提出两条合理化的建议:

a、                                                                  

b、                                                                  

阅读理解

(共5小题;每小题2分,满分10分)

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

It is your skin that keeps your insides from falling out. It helps you warm up when you are cold, and it can cool you off when you are hot. It lets you feel things by touch.

Like the heart, stomach and brain, your skin is an organ. In fact, it is the largest organ in your body. But it is still easy to take skin for granted.  1  But skin has an important job to do.

Your skin is constantly protecting you.   2  When you take care of your skin, you are helping your skin do its job. And taking care of your skin today will help prevent future problems, like wrinkles(皱纹) and even skin cancer.

3   Keeping your hands clean all the time is especially important because they can spread germs(细菌) to the skin on other parts of your body.

4   Cold or hot water may hurt your skin. Wet your hands, then lather up with a mild  soap (香皂). You should rub everywhere, including the palms, the wrists and the nails. Wash them well, dry thoroughly with a clean towel and you’re done.

You'll also want to use warm water when you take a bath. Use soap to clean your body. Don't forget under your arms and behind your ears! Your face needs attention, especially as you enter puberty(青春期) and the skin on your face gets more oily.  5 

A.One simple way to take care of your skin is to keep it clean.

B.It is a good habit to wash your hands before and after meals.

C.When washing your hands, use water that’s comfortably warm.

D.It keeps infections out of your body and keeps you from getting sick.E.     Unless there’s a problem, your may not think about your skin very much.

F.     Your skin plays a more important role in keeping you healthy during your puberty.

G.    It’s a good idea to wash your face once or twice daily with warm water and a mild soap.