Nitrogen ,`N_(2)`is fixed (converted to compounds)by

Options

A. bacteria
B. Lightning
C. the industrial synthesis of `NH_(3)`
D. All of these

Answer

4

Explanation

Most of the available nitrogen on earth is present as nitrogen gas (dinitrogen ,`N_(2)`) in the atmosphere ,Which consists of `78%` by volume. Dinitrogen (also simply called nitrogen) has collected in the atmosphere because of its relative chemical unreactivity.
Most organisms can't use `N_(2)`from the atmosphere as their source of the element .However, certain solid bacteria , as well as bacteria that live in nodules on the roots of beans, clover and similar plants can "fix" nitrogen , that is ,they convert dinitrogen gas to ammonium and nitrate compounds.
Plants use these simple nitrogen compounds to make proteins and other complex `N`compounds .Animals eat these plants, and other animals .Finally, bacteria in decaying organic matter convert the `N`compounds back to `N_(2)`, in the way, nitrogen in our environment continually cycles from `N_(2)` to living organisms and back.
The concept of `N_(2)` cycle also helps to understand that fact that `N` is found in the form of proteins in plants and animals.