State whether the following statement is true or false:
The process of nitrogen fixation is carried out by bacteria in the presence of oxygen.

(B) False.
Nitrogen fixation is carried out by nitrogen-fixing bacteria such as $Rhizobium$ and $Azotobacter$. The enzyme responsible for this process,nitrogenase,is highly sensitive to oxygen and is inactivated by it. Therefore,these bacteria perform nitrogen fixation under anaerobic (oxygen-free) conditions or by creating a specialized environment (like leghemoglobin in root nodules) to protect the enzyme from oxygen.