Concept:Land ecosystems are balanced by natural conditions, and climatic change is the main natural factor that disrupts or acts on this balance.
Explanation:Land ecosystems depend directly on rainfall, temperature, humidity, wind, and sunlight.
When climate changes, these factors begin to vary, and the variation disturbs the existing balance among plants and animals.
Such climatic change may be sudden, as in droughts or storms, or gradual, as in long-term warming or cooling.
In both cases, nature's most active and noticeable intervention in ecosystem balance happens through climatic change.
Earth's rotation and revolution are regular, predictable movements that do not, by themselves, intervene in ecosystem balance.
Even the idea of Earth equilibrium refers to physical stability, not to ecological adjustment.
Therefore, climatic change is nature's chief way of intervening in land ecosystem balance.
Answer:B. climatic change