单项选择题
A. could B. might C. succeeded to D. was able to
A．research showed their health benefits B．people got the. message from magazine covers and postage stamps C．scientific evidence of health benefits was shown on TV ads D．an increasing number of races were held in American cities
A．take care not to be over-critical in his writing B．watch carefully to see that nobody else takes his job C．be careful to ensure that his comments retain their value D．be sure that his salary keeps pace with inflation