'अर्बन हीट आइलैंड' (शहरी ताप द्वीप) प्रभाव को निम्नलिखित में से कौन सा विकल्प सर्वोत्तम रूप से वर्णित 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)?