Temper tantrums that often occur in children between the ages of eighteen months and three years of age are most likely caused by
a. a reaction to a food allergy.
b. the child being stubborn.
c. the child not liking their friends.
d. frustration over not being able to effectively communicate.

Bruh why would it be from a food allergy That's just ridiculous. The correct answer if D.

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.

industry had made the u.s. the richest nation in the world at this time. the second industrial revolution caused growth in industry and transportation, which allowed increased trade between nations.