题目内容：
根据以下材料，回答题Thebanana"tree"isactuallynotarealtree．Thisisbecausethereisnowoodinthestem(树干)risingabovetheground．Thestemismadeupofleavesgrowingveryclosetoge‘her，onemsldetheother．Theleavesspreadoutatthetopofthestemandriseintheair·
Bananaplantsneedalotofcareandattention．Theymustbeprovidedwithwaterifthenormalrainfalldoesn’tsupplyenough．Theareaaroundtheplantsmustbekeptfreeofweeds(杂草)andgrass．
Aboutnineortenmonthsafterplanting，aflowerappearsonthebananaplant.Thisflowerisattheendofalongstalk(茎)，whichgrowsfromthebaseupthroughthecenterofthestemandturnsdownwardwhenitcomesoutfromthetop．Smallbananasformonthisflowerstalkasitgrowsdown。ward．Bananasreallygrowupsidedown．Asthesmallbananasformonthestalk，theypointdownward．butastheygrowtheyturnandpointupward．
Bananasareharvestedwhiletheyarestillgreen．Evenwhentheyaretobeeatenwheretheyaregrown，theyarenotallowedtoripenontheplant．Abananathatturolsyellowontheplantlosesitstaste.
Thefirstparagraphinthetextmainlydiscusses. A．whvthestemofthetreeiswood
B．howthebananagrowsonthestem
C．whvthebananatreeisnotatree
D．howtheleavesgrowoutofthestem
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答案解析：