Which of the following plants does not have $Rhizobium$-containing root nodules?

Mark the correct sequence of steps for the development of root nodules in legumes:
$a.$ Formation of infection thread.
$b.$ Division of cortical and pericyclic cells.
$c.$ Curling of root hairs.
$d.$ Leghaemoglobin synthesis.

If a wheat field is inoculated with $Rhizobium$,what will be the effect on the soil?

We find that $Rhizobium$ forms nodules on the roots of leguminous plants. Also,$Frankia$,another microbe,forms nitrogen-fixing nodules on the roots of the non-leguminous plant $Alnus$. Is it necessary for a microbe to be in close association with a plant to provide mineral nutrition? Explain with the help of one example.

Symbiotic nitrogen fixation in non-leguminous plants is carried out by

Identify the $A$ to $D$ correctly in the given diagram of root nodule development and choose the correct option accordingly.