题目内容

The sudden up thrust of warm, moist air into the terrible cold of the frozen heights is what creates thunder. The sudden stronger rubbing together or two unlike forces (very warm air against very cold air) develops a kind of electricity called" static electricity". Its charges pro duce lightning and thunder. (46) Thus the violence of the thunderstorm is an almost direct result of millions of warm water drops being thrown into compatible masses of ice crystals--hitting them , rolling over them, melting them, or being frozen by them into snow or hail.Exactly how the electric charge is developed by the many, complex forces of this battle of heat and cold is still a matter of opinion. Some scientists think the action of wind against the rain is the principal factor. (47) These scientists believe the wind tears off the outer surface of each falling drops, like pulling a sweater over a child’s head, making a fine negative charge while leaving the main part of the rain drop positive. Other scientists believe that the friction of snow crystals breaking in the wind sets up the electrical charge. In reality it may well be all these factors--and more--that combine to do the work.(48) In any case, huge masses ’of electrically charged raindrops and hailstones become sorted into positive and negative reserves of electrical energy at different parts of the thundercloud, creating between them fields of very great extremes. When the resistance between these fields breaks down, the energy that is suddenly discharged is lightning.I do not know of any case of lightning directly causing an airplane accident, Cattle and sheep are more likely to be struck by lightning than are airplanes or houses. There is a recorded case that occurred on a mountainside in the western part of the United States in which one bolt of lightning killed 835 sheep. (49) Evidently the hard, dry earth offered more resistance to the lightning than the route of traveling from the ground, up one leg of an animal, through its moist’ body, and down another leg.A person’ s chances of being killed by a thunderstorm are not very great. In the United States an average of one person in 265000 dies as a result of a thunderstorm. Today houses, ships, airplanes, and electric power lines are well protected against lightning, and the. risk is de- creasing. Even a man whose work exposes him almost daily to lightning can do something about it. (50) Despite the saying that one never knows if lightning strikes him, a person can sometimes feel the bolt coming and, if quick enough take protective action in time. Despite the saying that one never knows if lightning strikes him, a person can sometimes feel the bolt coming and, if quick enough take protective action in time.

查看答案
更多问题

Beth: Did you hear that Ron was in the hospitalMimi: Oh, really (56) with himBeth: He’s got a very high temperature. I guess it may be cholera (霍乱).Mimi: Cholera! How in the world did (57) Beth: Who knows!Mimi: (58) for a long timeBeth: For a couple of weeks, apparently. But he only (59) on Monday.Mimi: Why did he wait so long He should have seen a doctor earlier.Beth: Yes, I know. But luckily the doctor says if he stays in the hospital for a few weeks, he should be able to improve.Mimi: Gee, (60) . 57()

男性,66岁,反复咳嗽、咳痰30余年,进行性呼吸困难10余年,反复双下肢水肿2年。因咳嗽、咳痰加重3天入院。查体:口唇发绀,颈静脉怒张,球结膜充血水肿,桶状胸,双肺叩诊呈过清音,呼吸30次/分,双下肺可闻及细湿啰音,双下肢呈可凹性水肿。病理反射未引出。胸片示:两肺纹理增重、紊乱,两肺透亮度增高。 患者查体示肝脏肋下4cm,下列哪项检查结果强烈提示肝脏肿大是由心功能不全所致

A. B超示肝被膜不光滑、脾大
B. 门脉内径增宽
C. 肝内胆管扩张
D. 肝内静脉扩张
E. 肝左叶增生

企业的存货周期减慢会影响流动比率的升高,不能以此为依据认为企业的偿债能力提高。()

A. 对
B. 错

目前IP地址是四组16位的二进制数字组成。

A. 对
B. 错

答案查题题库