The Crusades is the series of wars between the two groups but if you're looking for a certain one I can further elaborate.
Could you rephrase this question?
I think it's B. A reason to go to a place.
<span>fight to defend the polis</span>
During the 1800s and 1900s, the advancement of technology changes the way we do our daily activity
The same thing happen in our current period. The development of technologies and the advance of internet allow us to do a lot of remote jobs that we're unable to do before
hope this helps