What is the source of most atmospheric emissions of dioxins in North America? 

A)  landfills 
B)  refrigerator manufacturers 
C)  paper mills 
D)  medical and municipal solid-waste incinerators

What is one reason that polar bears are among the species most affected by global climate change? 

A)  They are having difficulty finding pack ice from which to hunt seals. 
B)  They are having difficulty finding suitable denning areas. 
C)  Their normal mating cycle has been disrupted. 
D)  The cubs are too warm because of their thick fur.

Although both are considered tropical cyclones,what is the difference between a hurricane and a typhoon?