4．（4分）请将下列胚的结构与将来的发育情况对应起来。

①子叶                       ②胚根                      ③胚轴                      ④胚芽

a根                           b茎、叶                    c连接根和茎的部分      d消失

①________________                                              ②________________

③________________                                           ④________________