How did the physical environment of river valleys negatively impact ancient civilizations? The land was attractive to outside invaders who wished to conquer the land. Rivers prevented the people from moving because they could not cross them. Occasionally, extreme flooding caused great damage and killed many people. Silt in the rivers made the water dirty and possibly unsafe for people to drink.

Which of the following statements best describes what is occurring in the land surrounding the sahara desert? a desertification is increasing, and the desert is expanding. b. fewer people are trying to farm in this semiarid region. c. the desert is shrinking with the increased use of irrigation. d. increased urbanization has resulted in decreased deforestation. select the best answer from the choices provided mark this and return save and exit next submit