Why are experimental investigations the best type of scientific investigation to demonstrate cause-and-effect relationship

answer; i believe the first answer to be (independent; /// and the second answer is (french); good luck

the factors that the economies of the muslim empires prosper were:

1- land trade routes-located between three continents  

2- sea trade routes

trade contributed to the spread of muslim empires, and with that islamic culture led to a growing feeling of internationalism resulted in the transfer of technology, science, and other cultural forms.