During the summer in the Arctic Ocean, sea ice ha, been melting earlier and faster, and the winter freeze has been coming later. In the last three decades, the extent of summer ice has declined by about 30 per cent. The lengthening period of summer melt threatens to undermine the whole Arctic food web, atop which stand polar bears.
Which among the following is the most crucial message conveyed by the above passage?
(a) Climate change has caused Arctic summer to be short but temperature to be high.
(b) Polar bears can be shifted to South Pole to ensure their survival.
(c) Without the presence of polar bears, the food chains in Arctic region will disappear.
(d) Climate change poses a threat to the survival of polar bears.