What is not a problem of that occurs during a drought

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.        

can you explain a little further maybe give multiple choice? ?

both focus ón people who behave in a risky way and çause accídeñ both explaín how to púrchase insurance añd cover the costs of premium. both describe what happened when consumers fail to pay their premíums in time