Investment in developing new skills for older workers is seen as a strategy .both for improving the quality of life for older adults and ______.

A．Viewing football games.
B．Interview with football players.
C．Attendance at track meets.
D．Types of college cheers.

A．A new fuel for buses.
B．The causes of air pollution.
C．Careers in environmental engineering.
D．A way to improve fuel efficiency in buses.