Choose the alternative which presents the correct prepositio...

When we think about global warming and climate change, we usually think ________________how it is going to affect humans. However, we need to think about animals, too. Many species will be threatened

______________________ extinction by the end of this century if climate change is not halted. One of these is the world’s largest land predator, the polar bear. This magnificent native ___________________ the Arctic previously had no natural enemy apart _______________________man, but is now under threat from nature itself. Because of melting sea ice, it is likely that more polar bears will soon starve, warns a new study that discovered the large carnivores need to eat 60 percent more than anyone had realized.

Polar bears use floating ice as a platform to hunt seals from. They eat a large volume of food during the winter, storing enough fat under their skin to last them through the summer months. When the ice melts in the spring, many travel south to places such as Churchill, Canada, returning north when the seas freeze again, usually around October. Now, however, the winter ice is melting earlier and forming later. The bears’ store of fat runs out, and some starve to death. Other bears are drowning, because many of the ice platforms have melted, and some bears have to swim over a hundred kilometres from one ice platform to another. Due to exhaustion or stormy weather, some never make it to their destinations.