Final answer:
The section "global warming is a threat" explains that scientists are concerned that rising temperatures will expose Antarctica's land.
Step-by-step explanation:
The section "global warming is a threat" explains that scientists are concerned that rising temperatures will expose Antarctica's land (option b). Global warming is causing the melting of the polar ice sheet over Antarctica, which could result in a considerable rise in sea levels. This section highlights the potential consequences of global warming on Antarctica and the rest of the world.