一个多边形的内角和是它的外角和的5倍，求这个多边形的边数．

Here you ____ (is/are).

根据句意及汉语提示完成单词.

① Have you____ (曾经)taken the subway alone late at night?  

②She won first____ (奖)in the 100-meter race.  

③It was his____ (梦想)to play football for his country.  

④We can not____ (付得起)the cost of two telephones.  

⑤It was a____ (遗憾)that you missed the party.  

如图为基因型为aaBbCc的某动物细胞分裂示意图，据此可确认该细胞（　　）

1859年达尔文发表巨著《物种起源》，提出了以____学说为核心的生物进化理论．