高一unit4新四省试验教材课件
日期：2010-09-06 09:14
Astronomy: thescienceofthestarsUnit411HowmanystarsarethereintheMilkyWay?Aabout100billionBabout200billionC20billion2Whatarethelargestobjectsthatcirclearoundthestars?AplanetsBsatellitesCgalaxies（银河）23Whendidtheearthcomeintobeing?Aabout10billionyearsagoBabout20billionyearsagoCabout45billionyearsago4Whendidlifebeganontheearth?Aabout1billionyearsagoBabout2billionyearsagoCabout3billionyearsago35ManyscientistsbelievethattheuniversebeganwithanenormousexplosioncalledtheBigBangWhendidithappen?Aabout15billionyearsagoBabout15billionyearsagoCabout4billionyearsagoHOWLIFEBEGANONTHEEARTHAinsectsandamphibiansappearBasolidballCreptilesappearDacloudofdustEshellfishandotherfishappearFdinosaursappearGsmallplantsgrowonthewaterHplantsbegintogrowondrylandIpresenceofwaterJ，
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