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Water is the"life blood"of our earth．Like air and sunshine,it is very important 31 living things．Without water,there can be 32 life on the earth．All animals and plants need water.Man also needs water．We need water to drink,to cook and to clean 33 ．It even 34 the greater part of our bodies． 　　Water is almost everywhere．Even in the 35 places of the world,there is water in the air．However．we can drink not seawater but fresh water．To make things even 36 ,people often 37 to keep the water clean．They throw rubbish into rivers,lakes or seas．So not all the fresh water is 38 for us to drink．We're short 39 water．Something must be 40 to stop this． ( )31．A．by B．to C．of D．towards ( )32．A．none B．not C．much D．no ( )33．A．himself B．our C．us D．ourselves ( )34．A．made of B．make C．makes up D．made in ( )35．A．driest B．wetter C．drier D．beautiful ( )36．A．best B．worse C．worst D．better ( )37．A．decide B．try C．fail D．take ( )38．A．clean enough B．enough clean C．enough good D．dirty enough ( )39．A．for B．in C．at D．of ( )40．A．do B．did C．doing D．done