Can anybody tell me or explain what does red line mean in social studies

What is the meaning of red line?

to cross the red line

The Red line, or "to cross the red line", is a phrase used worldwide to mean a figurative point of no return or line in the sand, or "a limit past which safety can no longer be guaranteed."

;p

answer; /// i believe the correct answer is (when one group has an extremely high score at pretest;

1. seasonal

2. frictional unenployment

3. the number of the labor force multiplied by 100 and then subtract the number of unemployed.

4. 4%

5. an increase in prices