That fellow ______ at long distance running.

A．many Americans have switched from hydrocarbon-based fuels to wood because the price of the latter has risen
B．some wood-burning stoves cost up to one hundred times more than others
C．catalytic combustors increase the amount of pollution caused by wood burning stoves
D．agitators are cheaper addition to wood-burning stoves than catalytic combustors

A．It enables the blind to live a more normal life.
B．It is mainly used to scan the area in front of the operator for obstacles.
C．Fast succession of bleeps indicates that the obstacle is near.
D．Its sound can warn other people of the blind man’s approac