Answer:
Global warming is an aspect of climate change, referring to the long-term rise of the planet's temperatures. It is caused by increased concentrations of greenhouse gases in the atmosphere, mainly from human activities such as burning fossil fuels, deforestation and farming.
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They were loosing their lands that's why we can choose a) weak leadership
The best pyramid for this is the biomass pyramid. That is because they show how much ecological material can be found at each trophic level, which then can be used to model how the matter flows through the ecosystem that is being analyzed.