题目内容：
Questionsarebasedonthefollowingpassage:
Thousandsofyearsago,inthemiddleofanocean,milesfromthenearestisland,anunderseavolcanobrokeout.Thehotliquidpiledhigherandhigherandspreadwiderandwider.Inthisway,anislandroseupinthesea.
Astimewenton,hotsunandcoolrainsmadetherocksplitandbreaktopieces.Seawavesdashedagainsttherock.Inthisway,soilandsandcameintobeing.
Nothinglivedonthenakedsoil.Andthenthewindandbirdsbroughtplantseeds,spidersandotherlittlecreaturesthere.Onlyplantscouldgrowfirst.Onlythey,insunlight,couldproducefoodfromthemineralsofthesoil,waterandair.Whilemanyanimalslandedontheisland,theycouldfindnofood.Aspiderspunitswebinvain,becausetherewerenoinsectsforitswebtocatch.
Insectscouldn'tstayuntiltherewereplantsforthemtoeat.Soplantshadtobethepioneerlifeonthisnewisland.
Thepassagecenterson（ ）. A．howanunderseavolcanobrokeout
B．howanislandroseupinthesea
C．howsoilwasformedonanewisland
D．howlifebeganonavolcano-producedisland
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答案解析：