正确答案: D

下胚轴伸长

题目：子叶出土的幼苗是种子萌发时由于( )的结果。

解析：D

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举一反三的答案和解析：

[单选题]卵细胞是雌配子，成熟的花粉粒是雄配子。( )

错误

解析：解析：“雄配子”可改为“雄配子体”或将“成熟的花粉粒”改为“精子”。

[单选题]关于电磁波，下列说法正确的是

变化的电场可以产生变化的磁场

[单选题]BWhen people hear a president speak, they seldom think about others helping to shape the presentation（报告）. Today, however, presidents depend on writers such as J. Terry Edmonds to help them communicate（交流）effectively. Edmonds is the first African American ever to work as a full-time speechwriter for a U.S. president; he is also the first African American to serve as director of speechwriting for the White House. His is an all-American story of success.

Edmonds graduated from Morgan State University in 1967.