For two individuals who engage in the same two productive activities, it is impossible for one of the two individuals to a. have a comparative advantage in both activities. b. have an absolute advantage in both activities. c. be more productive per unit of time in both activities. d. gain from trade with each other.

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.        

answer; /// the correct answer is (a) burned the city;

answer; protecting domestic national security; i believe this is correct,plz check first,good luck;

answerfacing ostracism from within one's tightly knit community;