Much research bas been done on interviews in general but journalistic interviewing as a specific field has unfortunately ______.

A．Fuel-efficient cars.
B．Air pollution caused by cars.
C．History of Automobile developments.
D．Electric-powered cars.

A．Speak very slowly but loudly.
B．Ask questions frequently.
C．Vary pitch, volume and speed of speech.
D．Keep the speech clear and concise.