Why was the use of coal an improvement on using human, animal, wood or water power for energy?

because they wanted to

Explanation:

because that what i learned

all of them lol cause theres no map

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.