What social issues caused civil unrest in america in the last half of the 20 century?

Which of the following statements about this graph is accurate? world grain production has increased in every year since 1950. the amount of grain grown between 1950 and 1980 decreased. world grain production has generally increased between 1950 and 2010. more grain was grown in 1950 than in any other year.

What would lead a historian to consider two events to have a relationship of correlation rather than causation

Which empire was called "the sick man of europe? "