事业单位的核心特征是（） A.非营利性 B.服务性 C.公共性 D.劳务性

关于《中华民国临时约法》的表述，哪一项是错误的？  [ ]

A．颁布于中华民国二年

B．规定中华民国的主权属于国民全体

C．确立了三权分立的政治制度

D．具有资产阶级共和国宪法性质

语文学科的属性有哪些？

如图所示，倾角为θ=30°的足够长的固定斜面上，在底端0处固定一垂直斜面的档板，斜面上OM段光滑，M点及以上均粗糙．质量为m的物块A在M点恰好能静止，有一质量为2m的光滑小物块B以初速度v0=

2gL

自N点滑向物块A，已知MN=L，AB间每次碰撞后即紧靠在一起但不粘连，每次AB与档板碰撞后均原速率弹回，求：

（1）A、B第一次碰撞后紧靠在一起的初速度v_AB；

（2）物块A在M点上方时，离M点的最大距离s；

（3）系统由于摩擦和碰撞所产生的总内能E．

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.

Paragraphs 2 and 3 are written to（）

A. discuss the causes of climatic irregularities

B. exemplify the abnormal effects of EI Nino

C. explain the way in which EI Nino develops

D. show the recent observations of scientists

并联电路的总电流为各支路电流（）。

A.之和

B.之积

C.之商

D.倒数和