把胚是完整且活的种子，播种在水分充足的环境下，种子没有萌发，原因可能是（ ）
①温度太低；②缺少空气；③缺少阳光；④没有肥沃的土壤．
A．①②
B．③④
C．②④
D．①③
种子萌发的外界条件是②适宜的温度、③充足的空气和①充足的水分．因为只有这三个条件同时具备时，种子内的营养物质才能转变成溶于水的物质被种子萌发时利用．而光照和土壤对种子的萌发没有直接的影响．因此种子没有萌发的原因是没有适宜温度和充足的空气．①②符合题意．
故选：A
根据下面短文内容，从方框中选择适当的词并用其正确形式填空，使短文完整、通顺。
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