The correct option is
A Both assertion and reason are true and the reason is the correct explanation for the assertion
The polar regions of the Earth are characterised by extremely cold temperatures and remain covered in ice around the year. The Arctic (North Pole) and Antarctic (South Pole) circles of the Earth are primarily considered as the polar regions and the average temperature in both these regions permanently remains below the freezing point of water.
Thus, animals surviving in these regions, like the polar bears of the Arctic, penguins of the Antarctic, seals, etc., require special adaptations to survive in the extreme cold conditions.
Being mammals, seals are warm-blooded animals or homeotherms that can maintain a constant body temperature, irrespective of the changes in the external temperature. This is achieved due to the presence of the fatty blubber that acts as an insulator and prevents the loss of body heat to the external environment.
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1335541/original_Blubber.png)
Figure : Blubber in seal
Apart from this, the seals have shorter extremities (limbs and ears) that reduce the amount of exposed surface area for heat loss (Allen's Rule). Heat loss or gain is a function of surface area. They have large volume and heat production in the body depends on its volume.
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1329110/original_Capture.PNG)
Thus, both assertion and reason are true and the reason is the correct explanation for the assertion.