问题详情

The last paragraph implies that
A．local and regional climates have not fluctuated so much since the glacial periods.
B．the future of agriculture depends on how land usages affect climate.
C．until recently, very little information was documented about changes and consequences of land usage.
D．current human transformations of the land surface is of almost unprecedented scale.请帮忙给出正确答案和分析，谢谢！