高压断路器多断口的并联电容是起（）作用 A.提高功率因数 B.滤去高次谐波 C.多断

近来，整治互联网低俗之风专项行动取得了良好效果，显示了政府根治网络低俗之风的决心。在这场净化网络环境的斗争中，政府的威望和公信力得到人民的认同。此举表明我国政府的权威体现在                                  [ ]

①依法行政，维护宪法和法律的尊严，维护人民群众的根本利益②代表人民行使国家权力，决定全国和各级地方的一切重大事务③讲信誉，有令必行，有禁则止，得到人民的自觉认可和拥护④依法执政，体现审时度势的忧患意识和执政为民的责任意识  

A．①②    

B．②③  

C．①③  

D．②④

下面不是自凝成型的方法是（）。

A．涂塑成型

B．气压成型

C．加压成型

D．注塑成型

E．加温加压成型

现有下列短周期元素性质的数据，下列说法正确的是

	①	②	③	④	⑤	⑥	⑦	⑧
原子半径(10-10m)	0.74	1.60	1.52	1.10	0.99	1.86	0.75	0.82
最高或最低化合价	-2	+2	+1	+5；-3	+7；-1	+1	+5； -3	+3

A．⑧号元素为Al                           

B．②、③处于同一周期

C．上述八种元素最高价氧化物对应的水化物⑤号酸性最强       

D．④元素的气态氢化物沸点大于⑦元素的氢化物

环境问题的实质是 （   ）

A．人口问题

B．资源问题

C．发展问题

D．生态问题

El Nino is the term used for the period when sea surface temperatures are above normal off the South American coast along the equatorial Pacific, sometimes called the Earth’s heartbeat, and is a dramatic but mysterious climate system that periodically rages across the Pacific.

El Nino means "the little boy" or "the Christ child" in Spanish, and is so called because its warm current is felt along coastal Peru and Ecuador around Christmas. But the local warming is just part of an intricate set of changes in the ocean and atmosphere across the tropical Pacific, which covers a third of the Earth’s circumference. Its intensity is such that it affects temperatures, storm tracks and rainfall around the world.

Droughts in Africa and Australia, tropical storms in the Pacific, torrential rains along the Californian coast and lush greening of Peruvian deserts have all been ascribed to the whim of EI Nino. Until recently it has been returning about every three to five years. But recently it has become more frequent--for the first time on record it has returned for a fourth consecutive year--and at the same time a giant pool of unusually warm water has settled down in the middle of the Pacific and is showing no signs of moving.

Climatologists don’t yet know why, though some are saying these aberrations may signal a worldwide change in climate. The problem is that nobody really seems sure what causes the El Nin o to start up, and what makes some per than others. And this makes it particularly hard to explain why it has suddenly started behaving so differently.

In the absence of EI Nino and its cold counterpart, La Nina, conditions in the tropical eastern Pacific are the opposite of those in the west. the east is cool and dry, while the west is hot and wet. In the east, it’s the winds and currents that keep things cool. It works like this. Strong, steady winds, called trade winds, blowing west across the Pacific drag the surface water along with them. The varying influence of the Earth’s rotation at different latitudes, known as the Coriolis effect, causes these surface winds and water to veer towards the poles, north in the northern hemisphere and south in the southern hemisphere. The surface water is replaced by colder water from deeper in the ocean in a process known as upwelling.

The cold surface water in turn chills the air above it. This cold dense air cannot rise high enough for water vapor to condense into clouds. The dense air creates an area of high pressure so that the atmosphere over the equatorial eastern Pacific is essentially devoid of rainfall.

The writer begins the text with（）

A. a description of a scene

B. a root cause of EI Nino

C. a narrative of an event

D. a definition of EI Nino