If the temperature at the earth's surface is twenty degrees Fahrenheit, the temperature in a coal mine 500 feet below the surface would, in degrees, be _____________.

A．interior of the earth
B．results of volcanic action
C．work of geologists
D．formation of volcanoes

A．Vendors should lay great importance on service.
B．Hardware will account for a greater share of computer companies' revenue.
C．Trends of the 1990s in computer industry are difficult to predict.
D．Manufactures of monitors and printers will expand their business to automobile industry.