This cold war enemy of the united states "collapsed" in 1991 after years of economic and political turmoil

The Soviet union was the Cold War enemy of the United States that collapsed in 1991 after years of economic and political turmoil.

Explanation:

answer:

d. because dr. laguardia selected a widely used measure, his study generalizes to has strong external validity. external validity has limited external validity. other applications of this measure.

the widely used measure that he applied to his experiment was the benton facial recognition test. it employed on to football players and as result, only players who suffered brain concussions did not pas this test. and although it has an external validity, it is limited because it isn't general to apply to other population.

answer; i believe the correct answer is (crops);