A．They believed that the resources would decline.
B．They knew that the resources would soon be exhausted.
C．They argued that the resources were limited.
D．They assumed that the resources were unlimited.

A．They are important food resources.
B．The great fisheries are to be exhausted.
C．Noted biologists insist on their maintenance.
D．Fishes are fewer than American eagles.

A．They are endangered on land or in the air.
B．They are important species for conservation.
C．They are symbols of different countries.
D．They are examples of zoo animals.