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.