Which of the following, if true, gives the best explanation for the growing disparity in the earning levels of the two groups in the graph presented above

单项选择题Currently, the number of first-time admissions of individuals diagnosed as manic-depressives to hospitals in Great Britain exceeds by nine times the number of admissions of such patients to public and private hospitals in the United States, even though the population size of the United States is many times that of Great Britain. Which of the following, if true, would be most useful to an attempt to explain the situation described above ？（）

A．The term manic-depressive refers to a wider range of mentally ill patients in Great Britain than it does in the United States.
B．The admission rate in the United States includes those individuals who visit clinics for the first time as well as those who are admitted directly to hospitals.
C．A small percentage of patients diagnosed as manic-depressive in Great Britain are admitted to private nursing homes rather than hospitals.
D．The variety of training institutions in psychology in the United States is greater than in Great Britain, reflecting the variety of schools of psychology that have developed in the United States.
E．Seeking professional assistance for mental health problems no longer carries a social stigma in the United States, as it once did.

单项选择题Regional and local telephone companies around the nation are beginning to offer customers an electronic operator system that allows customers to choose to make some operator-assisted calls through an electronic operator. Nevertheless, the number of human operators on staff will not be reduced in the foreseeable future. Each of the following statements, if true, helps explain why the number of human operators is not being reduced EXCEPT （）.

A．Demand for operator-assisted calls is increasing dramatically.
B．The new electronic operator system, though it has been tested, is expected to require significant adjustments before it can become fully operational.
C．The operators union would be quick to strike the companies involved if operators were dismissed during the current contract period.
D．In one regional trial of the electronic system, virtually all consumers, given a choice, preferred a human operator to an electronic one.
E．The new electronic operator system will complete operator-assisted calls twice as fast as human operator can.