生殖隔离的形成包括以下哪几种                                    （    ）
①动物因求偶方式、繁殖期不同造成不能交配
②植物因开花季节、花的形态不同而不能交配
③动物胚胎发育早期死亡
④产生的杂种后代没有生育能力

完形填空
    This is an educational story．A teacher once told each of her students to bring an empty plastic bag and a large bag of 1 to school．If there was someone in their lives that they 2 to forgive，they chose a potato，  3  the name of that person and the date on it, and then put it  4 the plastic bag．Some of their bags were quite heavy．
    They were then told to5 these bags with them everywhere for one week，putting them beside their beds  6 and next to their desks in the classroom．
    As they carried the bags around with them，they 7 what a weight they were carrying，and how hard they needed to pay attention  8 ． Of course，the potatoes were rotten(腐烂的)soon，and smelled  9 ．
    This is the same as the price we pay for keeping our pain and unhappiness with us!So 10others is not only a gift for them，but also a very good gift for ourselves．

下图显示纯合体的棕毛豚鼠（雄）与纯合体黑毛豚鼠（雌）交配后产生下一代的遗传结果请据图分析回答。（用T、t表示控制皮毛颜色的显、隐性基因）

 

关于公式 R＝，下列说法中正确的是（）

京津冀地区位于环渤海地区的中心位置，是国家经济发展的重要引擎和参与国际竞争合作的先导区域，京津冀协同发展是重大国家战略。下图为“京津冀产业特征及联系示意图”。读图，回答下列各题。