古埃及、古印度、古巴比伦和古中国被称为四大文明古国。它们产生的环境的共同点是（　　）

阅读下列古诗答题。

                                                                                                                                       《绝句》
                                                                                                                                          唐·杜甫
                                                                                                                           迟日江山丽，春风花草香。
                                                                                                                           泥融飞燕子，沙暖睡鸳鸯。
       【注释】泥融：指冻泥融化，又软又湿。