ReadthefollowingpassageandmarktheletterA,B, C,orD onyouranswersheettoindicatethecorrectanswertoeachofthe questions.

Themineralparticlesfoundinsoilrangeinsizefrommicroscopicclay particlestolargeboulders.Themostabundantparticles-sand,silt,andclay-are thefocus of examination in studies of soil texture.Textureis the term used todescribethelinecompositesizesofparticlesinasoilsample,typically severalrepresentativehandfuls.Tomeasuresoiltexture,thesand,silt,andclay particlesaresortedoutbysizeandweight.Theweightsofeachsizearethen expressed as a percentage of the sample weight.

Inthefield,soiltexturecanbeestimatedbyextractingahandfulofsodand squeezingthedampsoilintothreebasicshapes;(1)cast,alumpformedby squeezingasampleinaclenchedfist;(2)thread,apencilshapeformedby rollingsoilbetweenthepalms;and(3)ribbon,aflatfishshapeformedby squeezing a small sample between the thumb and index finger. The behavioral characteristicsofthesoilwhenmoldedintoeachoftheseshapes,iftheycanbe formedatall,providesthebasisforageneraltexturalclassification.The behaviorofthesoilinthehandtestisdeterminedbytheamountofclayinthe sample.Clayparticlesarehighlycohesive,andwhendampened,behaveasa plastic.Thereforethehighertheclaycontentinasample,themorerefinedand durable the shapesinto which it can be molded.

Anothermethodofdeterminingsoiltextureinvolvestheuseofdevicescalled sedimentsieves,screensbuiltwithaspecifiedmeshsize.Whenthesoilis filteredthroughagroupofsieves,eachwithadifferentmeshsize,theparticles becomegroupedincorrespondingsizecategories.Eachcategorycanbe weighedtomakeatexturaldetermination.Althoughsievesworkwellforsilt, sand,andlargerparticles,theyarenotappropriateforclayparticles.Clayisfar toosmall tosieve accurately;therefore, insoilswith a highproportion of clay, thefineparticlesaremeasuredonthebasisoftheirsettlingvelocitywhen suspendedinwater.Sinceclayssettlesoslowly,theyareeasilysegregatedfrom sandandsilt.Thewatercanbedrawnoffandevaporated,leavingaresidueof clay, whichcan be weighed.

What is true of Lake Vostok?