Getting better on a task in a study with practice can cause a source of bias called

I believe the answer is: testing effects

Testing effects refers to the perception long term memories tend to be increased when our brain is dedicated to retrieving a certain type of information over and over again. When studying, this tend to make people become bias and overconfident after repeating a certain topic, making them believe that they do not need to study the topic again before test.

most cajuns resided in acadiana, where their descendants are still predominant

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.