1940 के दशक में प्रकाश-रासायनिक स्मॉग (Photochemical smog) पहली बार किस शहर में देखा गया था?

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)?