[单项选择]
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All along the chain of
biological evolution, the extinction of species appears to have been a stage in
the process of adapting genetic lineages to changing environmental conditions.
Although some catestrophic extinction occurred naturally, producing total loss
of a genetic line, such catastrophes were comparatively rate. In modern times,
however, human activities have altered the fundamental nature of this process,
resulting in nearly total genetic losses.
It is not difficult to
gain general agreement that man - induced increases in the endangerment and
extinction of wildlife--whether due to habitat alteration or loss, pollution,
insufficiently regulated hunting, or other factors--are undesirable. It is,
however, more difficult to obtain consensus when consideration is given to the
economic costs of correcting such trends, including natural habitat
preservation, regulation of pesticides and other toxic substa
A. have revealed little of importance to improve wildlife preservation
B. are more likely to be carried out when a financially concerned interest group is involved
C. sometimes endanger the very species they hope to protect
D. show that endangered species can never be saved except at great cost
