The correct answer is - c. Unrestricted whaling could lead to their extinction.
Most of the whale species are on the endangered list, which means that they have very low number of individuals which puts them in risk of being extinct. The restriction of the whaling must be respected by all countries in order for the whales to have a safe future and be preserved as a family.
All of the countries in the world have signed and agreed to stop the whaling, and only two refused, surprisingly enough, it is Norway and Japan that do not signed and continue with whaling. Even though most of the waters are nowadays safe for the whales, the problem is that some species migrate in waters that belong to Japan and Norway, and that damages their populations.