Well, uniting against a common enemy has always been a great unifier. Plus, literally fighting for freedom made every person fighting believe very deeply in their cause, and so they could overcome differences with each other for that cause.
Answer:
D provide important services
Selection bias
is a kind of error that occurs when the researcher decides who is going to be studied.
Answer:
for everyone one to be equal
Explanation:
Just added answer for corrupted so he could get brainliest