进行有性生殖的生物，对维持其前后代体细胞中染色体数目恒定起重要作用的生理活动是（　　）

邓小平在一次参观文物展览时，指着一幅名画说：“我们祖先早已熟知商品经济了。”这幅名画应是

①对人不讲理，很难与别人友好相处

②是否文明礼貌，不仅仅是个人的私事和小事

③传统的礼仪必须适应现代社会发展的需要

④外交礼仪周全，各国就能相互尊重与文明交往

    Hi, my name is Sam. I have a big family. Charles is my father and Janet is my mother. I have two sisters. My sister Sara is 16. Anna is 14. I'm the youngest in my family. I'm 11.

    Hi, my name is Charles. My parents are Paul and Susan. I have one brother and one sister. Gary is my brother's son. My sister Laura has two daughters. They are Dina and Kate.

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