In the United States, the (21) to protect plant and animal (22) has become a (23) controversial and (24) political issue since the (25) of the Endangered Species Act in 1973. The act, (26) to protect species’ living areas, and policies that (27) land and forests compete with economic interests.
In the 1990’ s, for example, the woodcutters in the Western United States were (28) legally in their (29) to cut trees for timber in the Cascade Mountains. The challenge was (30) to protect the endangered spotted owl, whose remaining population occupies these forests and (31) the intact, ancient forest for survival. The problematic situation set the interests of environmentalists (32) those of corporations and of individuals who (33) to lose jobs. After months of debate and legal battles, the fate of the woodcutters-and the owls was still undecided in mid-1992.
Similar (34) exist between the developed and the developing nations. Many people in industrialized nations, for example, believe that developing nations in tropical regions should do more to protect their rain forests and other natural areas. But the developing countries may be (35) , with populations growing so rapidly that using the land is a (36) to temporarily avoid worsening poverty and starvation.
Many of the changes to Earth that (37) scientists have the potential to (38) the planet of its biological richness. The destruction of Earth’ s ozone layer, for example, could (39) to the general process of impoverishment by allowing ultra-violet rays to harm plants and animals. And global warming could (40) species unable to quickly adapt to changing climates. Clearly, protecting will come only through coordinated international efforts to control human population, stabilize the composition of the atmosphere, and preserve intact Earth’s complex web life.

22（）

A．kinds
B．species
C．sorts
D．types