I'm not sure that I can explain all eight, but I'll give you my best answers.
A river valley is critical to early civilization because it provides direct food resources (fish, turtles, etc.), agriculture through diversion of river water (irrigation), faster, easier, and larger trade avenues (you can carry more goods in a boat than on a camel, and you can carry them farther and faster). Might consider that a central government could be maintained through use of the river to rapidly move military and police forces across large areas. If people don't have to put so much time into finding food anymore, then there is more time to specialize in other jobs (such as working in a stone quarry, or being a carpenter, etc.). Again, if you have more time on your hands, then you can go into "unnecessary" things, like art and architecture. I suppose that depending on which specialized jobs people go into, that might create social classes (but it would probably be different from civilization to civilization, because each society would put more importance into one thing than another society - for instance Sparta and Athens were very similar in ancient Greece, but in Sparta, it was more important to be a warrior, and in Athens, it was more important to be a scholar). Writing, again, could flourish simply because people have more time on their hands. Public works might arise because, as people's lives improve and get more sophisticated (because, for instance, people have more time to study science and engineering), they expect more, such as plumbing, or common buildings (perhaps a library or place of worship).
Those are my best explanations. An anthropologist could undoubtedly give you a better answer, but these at least seem reasonable.
As for complex religion? I have no idea how to approach that one. Sorry about that.
