Why people in Mesopotamia started Living in cities and how they solved problems that arose

Which of the following is a complex sentence? a. after henry submitted his essay, he realized that he hadn't proofread the last page. b. identity theft is a growing problem, especially among seniors. c. we didn't have enough potatoes for dinner, so we served rice instead. d. jim tried to watch a video on a device connected to a crowded wireless network; as a result, the video stuttered and froze.

What is meant by “eternally burning black pipes”? what is this implying about the personality of the firemen?

2. page 1: schlosser describes "just another gorgeous rocky mountain vista. and yet cheyenne mountain is hardly pristine." why do you think schlosser describes the beautiful cheyenne mountain scene in detail before describing the military installation that lies inside?