निम्नलिखित में से कौन सा ऊर्जा का एक गैर-पारंपरिक स्रोत है जो बिजली पैदा करता है?

Prolonged exposure to extreme cold temperatures may result in tissue damage known as frostbite, which is categorized as a:

In the context of ecosystem energy dynamics, which of the following expressions correctly defines Net Primary Productivity (NPP)?