Deep inside a mountain near Sweatwater in East Tennessee is a body of water known as the Lost SeA.It is listed by the 'Guinness Book of World Records' as the world's largest underground lakE.The lost Sea is part of an extensive and historical cave system called Craighead Caverns.
The caverns have been known and used since the days of the Cherokee Indian Nation. The cave expands into a series of huge rooms from a small opening on the side of the mountain. Approximately one mile from the entrance, in a room called 'the Council Room', many Indian artifacts have been founD.Some of the items discovered include pottery, arrowheads, weapons and jewelry.
For many years there were persistent rumors of a large underground lake somewhere in a cave, but it was not discovered until 1905. In that year, a thirteen-year-old boy named Ben Sands crawled through a small opening three hundred feet undergrounD.He found himself in a large cave half filled with water.
Today tourists visit the Lost Sea and ride far out onto it in glass-bottomed boats powered by electric motors. More than thirteen acres of water have been mapped out so far and still no end to the lake has been founD.Even though teams of divers have tried to explore the Lost Sea, the full extent of it is still unknown.
According to the passage, the lost Sea is unique because it is ______.
A.part of a historical cave system
B.the biggest underground lake in the world
C.listed in the 'Guinness Book of World Records'
D.the largest body of water in Tennessee

单项选择题叩击类手法中，用力最重、刺激量较强的手法是 A、叩法 B、击法 C、拍法 D、弹法

判断题发现触电后，可以直接用手去把触电人拉开。

单项选择题双向公交站迎面错开布置时，由于公交车体积较大，很容易阻挡其左侧机动车司机和右侧过街行人的视线，从而导致交通事故的发生。（ ） A. 对 B. 错

问答题汽油滤清器的主要作用就是过滤汽油中的杂质，使进入发动机内部燃烧的汽油干净，燃烧更充分，减少缸内的（ ）形成。

未分类题Volcanic fire and glacial ice are natural enemies. Eruptions at glaciated volcanoes typically destroy ice fields, as they did in 1980 when 70 percent of Mount Saint Helens ice cover was de molisheD.During long dormant intervals, glaciers gain the upper hand cutting deeply into volcanic cones and eventually reducing them to rubblE.Only rarely do these competing forces of heat and cold operate in perfect balance to create phenomenon such as the steam caves at Mount Rainier Park.Located inside Rainier's two ice-filled summit craters, these caves form. a labyrinth of tunnels and vaulted chambers about one and one-half miles in total length. Their creation depends on an unusual combination of factors that nature almost never brings together in one placE.The cave-making recipe calls for a steady emission of volcanic gas and heat, a heavy annual snowfall at an elevation high enough to keep it from melting during the summer, and a bowl-shaped crater to hold the snow.Snow accumulating yearly in Rainier's summit craters is compacted and compressed into a dense form. of ice called firn, a substance midway between ordinary ice and the denser crystalline ice that makes up glaciers. Heat rising from numerous openings (called fumaroles) along the inner crater walls melts out chambers between the rocky walls and the overlying ice pack. Circulating currents of warm air then melt additional opening in the firn ice, eventually connecting the individual chambers and, in the larger of Rainier's two craters, forming a continuous passageway that extends two-thirds of the way around the crater' s interior.To maintain the cave system, the elements of fire under ice must remain in equilibrium, Enough snow must fill the crater each year to replace that melted from below. If too much volcanic heat is discharged, the crater' s ice pack will melt away entirely and the caves will vanish along with the snows of yesteryear. If too little heat is produced, the ice replenished annually by winter snowstorms will expand, pushing against the enclosing crater wails and smothering the present caverns in solid firn icE.With what topic is the passage primarily concerned?A.The importance of snowfall for Mount Rainier.B.The steam caves of Mount Rainier.C.How ice covers are destroyeD.D.The eruption of Mount Saint Helens in 1980.