Today,ultrasonic(超声的)wavesarebeingputtoworkinlaboratoriesandfactories.Ifanultrasoundgeneratorisplacedinaliquid,thewavesmovetheliquidbackandforthhundredsofthousandsoftimeseachsecond.Thiscausesmaterialstomixquicklyortodissolve(使分解，使溶解)inliquids.Paintmanufacturers(制造商)useultrasoundtodoabetterjobofblendingcolors.Thecompaniesthatmakefilmforyourcamerafindthatmixingchemicalsbytheuseofsoundwaveswillproduceamoresensitivefilm.

Thenewlightweight(轻量的)typeofwashingmachineusesultrasonicwavestogetclothesclean.Itsspecialultrasoundgeneratorisputintoapailofsoapywatercontainingthesoiledclothes.Thesoundwavesdrivethesoapywaterbackandforththroughtheclothsofastthateverythingissoonclean.Thereisalsoanewkindofdishwasherthatworksinmuchthesameway.

Ultrasonicwavescanshakealiquidsofastthattinyholesformallthroughit.Theliquidisactuallytornapartbythisaction.Almostassoonastheseholesaremade,theyfalltogetheragain.Theresultisapowerfulpoundingaction.Inthedairyindustrythisisusedforthedoublepurposeofmakinghomogenized(使均匀，使匀质)milkandsterilizing(使无菌)itatthesametime.Ifyoulookatsomerawmilkwithamicroscope,youfindthatitismadeupoflittledropsofbutterfatfloatingaroundinawateryliquid.Inordertomakemilkeasiertodigest,thesefatdroplets(微粒)maybebrokenupbyforcingthemilkthroughverysmallopenings.Theresultiscalledhomogenizedmilk.Whentheultrasonicmethodisused,thesoundwavesnotonlybreakupthedropletsbutalsokillthegermsinthemilkbypoundingthemtopieces.(fromwww.nmet168.com)

1.Whydoesapaintmanufactureruseultrasoundtodoabetterjobofblendingcolors?

A.Becauseitischeaptouseultrasoundtoblendcolors.

B.Becausethewavesmovetheliquidsoquicklythatitcanmakematerialsmixquicklyordissolveinliquids.

C.Becausetheycanmixchemicalsbytheuseofsoundwaves.

D.Becausethewavescancleanthepaint.

2.Whatpropertiesdoesultrasoundwavehave?

A.Homogenizesandsterilizesthemilk. B.Mixmaterialsandbreakdroplets.

C.Killgermsandsterilizemilk. D.Moveliqu