निम्नलिखित में से कौन सा जोड़ा दो प्राथमिक वायु प्रदूषकों (primary air pollutants) को दर्शाता 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)?