A:however
B:whatever
C:whichever
D:whenever
____ + ____ = ____
绿色植物的受精过程依次是( )
①精子与卵细胞结合;②花粉管进入子房;③花粉管进入胚珠;④花粉萌发出花粉管;⑤花粉管末端破裂放出精子