A．attempts to find efficient ways of recycling wastes
B．efforts to protect the environment in British cities
C．a good way to locate plants for waste recycling
D．a cheap way to get energy from waste materials

A．The concept of "old" is differently defined in different times.
B．Nobody can remain physically healthy throughout the life.
C．The progress in medical knowledge has contributed a lot lo longer lives of us.
D．Older people may get ill and physically disabled more easily than younger ones.