同一等高线上____ 相同，等高线越密集，坡越____  ；越稀疏，坡越____ 。

已知：白磷的着火点为40℃，红磷的着火点为240℃

阅读下面的诗文，回答相关问题。

                                                                                                          《饮酒》
                                                                                                            陶渊明

                                                                                             结庐在人境，而无车马喧。
                                                                                             问君何能尔，心远地自偏。
                                                                                             采菊东篱下，悠然见南山。
                                                                                             山气日夕佳，飞鸟相与还。
                                                                                              此中有真意，欲辩已忘言。

蛙的生殖和发育过程要经历几个发育时期（　　）