Which of the following statements best explains what researchers have discovered about the cause of the fall of the maya civilization? a. diseases brought by european settlers wiped out the maya population. b. a drought in the maya region killed all of the crops and left people without food. c. constant wars among city-states killed many of the maya people. d. the reason for the fall of the maya civilization is still unknown.

D. The reason for the fall of the Maya civilization is still unknown. There are many  different theories  attempting to explain the cause of the Classic Maya collapse and the abandonment of Maya cities in the southern Maya lowlands of Mesoamerica between the 8th and 9th centuries: climate change, drought, deforestation, etc. but although the drought is the leading theory at the moment the truth is yet unknown.

the answer to your question is true