निम्नलिखित में से कौन सा अपशिष्ट बैक्टीरिया या अन्य मृतोपजीवियों (saprophytes) द्वारा विघटित नहीं किया जा सकता है?

The ozone layer in the stratosphere shields the surface of the Earth from which harmful radiations?

Sewage is mainly a:

Materials that cannot be broken down by the action of bacteria or saprophytes, but are degraded very slowly by physical processes, are called: