The discovery of gold in the valleys will ______ the poor mountain area.

A．America's machine-tool industry was losing its market.
B．America' s machine-tool industry was facing strong competition.
C．America's machine-tool industry was losing its position.
D．America's machine-tool industry was in danger.

A．It is human nature to shift between self-doubt and blind pride.
B．Intense competition may contribute to economic progress.
C．The revival of the economy depends on international cooperation.
D．A long history of success may pave the way for further development.

A．Pollution -- the Necessary Evil
B．The Causes of Pollution
C．Pollution and Agriculture
D．Anti-pollution Needs Your Efforts