英语改错题
WATER
Thesecondmostimportantconstituentofthebiosphereisliquidwater.Thiscanonlyexist
inaverynarrowrangeoftemperatures,sincewaterfreezesat0℃andboilsat100℃.Thisisonlyatinyrangecomparedwiththelowtemperaturesofsomeotherplanetsandthehotinteriorof
theearth,letthetemperatureofthesun.[26]
Asweknow,lifewouldonlybepossibleontheface[27]
ofaplanethadtemperaturessomewherewithinthis[28]
range.Theearthssupplyofwaterprobablyremainsquitefairly[29]
constantinquantity.Acertainnumberofhydrogenatoms,whichareoneofthemainconstituentsofwater,arelostbyescapingfromtheatmospheretooutspace,buttheyareprobablyjustaboutreplacedbynew[30]
waterrisingawayfromthedepthsoftheearthduring[31]
volcanicaction.Thetotalquantityofwaterisnotknown,anditisaboutenoughtocoverthesurfaceoftheglobe[32]
toadepthofabouttwoandthree-quarterkms.Mostofit——97%——isintheformofthesaltwatersoftheoceans.Therestisfresh,butthreequarterofthisis[33]
intheformoficeatthePolesandonmountains,andcannotbeusedbylivingsystemswhenmelted.Ofthe[34]
remainingfraction,whichissomewhatfewerthan1%ofthe[35]
whole,thereis10-20timesasmuchstoredasundergroundwaterasisactuallyonthesurface.Thereisalsoaminor,butextremelyimportant,fractionofthewatersupplywhichispresentaswatervaporintheatmosphere.