How did people in medieval Japan increase their farmable land

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.        

the values of the selma marchers was to bring   their ability to vote into law. mlk was not hat march, which was protesting toward lbj

answer; the above statement is (true);