In relation to the cognitive development theory, piaget proposed that the concrete operational stage lasts from approximately years of age.

a) 6-10 b) 7-11 c) 8-12 d) 9-12

b) 7-11                                                  

Explanation:

Jean Piaget has proposed the cognitive development theory in which he has mentioned four different stages of an individual's life including the sensorimotor, preoperational, concrete operational, formal operational stage.

Concrete operational stage: In cognitive development theory, this is considered as the third stage and starts from the seven years of a child's age and lasts through eleven years i.e, the middle childhood period. The concrete operational stage is distinguished as the development of a child's logical thought, cognitive limitations, conservation, etc.

In the question above, the given statement signifies the age between 7-11.

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.