What is one way to address the threat of global warming? 

A)  using energy more efficiently 
B)  shifting to non-renewable resources 
C)  increase clear-cutting in tropical forests 
D)  halting deforestation

Using energy more efficiently can reduce the amount of greenhouse gas emissions that contribute to global warming. This can be achieved by adopting alternative energy sources, improving energy efficiency in buildings, and implementing policies to reduce energy consumption. Shifting to non-renewable resources or increasing clear-cutting would only worsen the problem of global warming, while halting deforestation can help combat climate change but is only addressing one aspect of the issue. Therefore, the best choice is A - using energy more efficiently.