A major threat to the internal validity (esp. time-related threats and order effects) for pre-post designs can occur as it is impossible to
a. randomly assign participants.
b. counterbalance the order of treatments.
c. control for differential effects.
d. generalize the results.

every society, in order to meet the needs of it's people, has to answer three basic questions:

- what should we produce?

- how should we produce it?

- for whom should we produce it?

this questions must be answered in order to, option b, aid in production decisions.

every country can't produce everything, no matter how rich their land is. it may be a matter of technology, resources or geographical conditions. so, these three questions must be resolved in order to get the most of the production of each land.

hope this !

the answer is:

c. economic output

answer; i believe the correct answer is prefrontal cortex;