Root nodules for nitrogen fixation in non-leguminous trees are produced by species of the genus

Assertion : Leguminous plants are nitrogen fixers.
Reason : Leguminous plants have $Rhizobium$ in their root nodules.

Leguminous plants have the ability to fix atmospheric nitrogen through a symbiotic nitrogen fixation process. Which of the following statements is $NOT$ true regarding this process?

Which kingdom of organisms is responsible for the development shown in the plant below?

With reference to the root nodules shown in the following diagram,select the correct option.

Explain the stages of root nodule formation.