How many significant demographic changes ever occurred in the past one million years

A．Human population expands at an exponential rate.
B．Population growth has shown fluctuation in demographic history.
C．Population growth can not be regarded as a social failure.
D．Increase in population is related to productivity.

A．their preoccupation with profits overlooks the need for more humanistic values
B．their lawyers are ignorant of international trade laws
C．there is a great need for physicians
D．they have not been able to make the best use of their own resources