下列反应的离子方程式中，正确的是                                      

下列过程中，没有发生膜融合的是（   ）

  1时＝100分。

选择恰当的句子补全对话。
A：Can I help you?
B：Yes，please. ____ This yellow dress is pretty.How much is it?
A：It's forty yuan.
B：It's cheap. ____
A：Sure！Here you are.
B： ____
A：Do you like that red one?
B： ____
A：It's ninety yuan.
B： ____
A．It's too big.
B．Can I try it on?
C．How much is it?
D．I want to buy a dress.
E．Oh，it's too expensive for me.

历史上外戚专权的事件非常多，汉朝就是一个典型。到了南北朝时期这种现象依然存在，如果你穿越时空到达北朝的北周末年，你会看到哪位外戚专权（　　）