Which part of the world did NOT experience the negative population growth

A．Dennis was blind at birth
B．Dennis was younger than anyone else he could find
C．Dennis’s parents were quite worried about his future
D．Dennis always produced sharp clicking sounds with his tongue

A．shouldn’t replace "scientific method" with imaginative thought
B．shouldn’t neglect to speculate on unpredictable things
C．should write more concise reports for technical journals
D．should be confident about their research findings