Nodules with nitrogen-fixing bacteria are present in

Which of the following are the part or example of symbiotic mutualistic association?
$I.$ Yeast
$II.$ Rhizobium
$III.$ Mycorrhiza
$IV.$ Oscillatoria

Arrange the stages of root nodule formation in the correct sequence:
$I-$ Infection thread is produced.
$II-$ Bacteria are carried to the cortex of the root.
$III-$ Bacteria attach to the root hair.
$IV-$ Bacteria are released from the thread into the cells.
$V-$ Differentiation into nitrogen-fixing cells occurs.

Which steps are associated with nodule formation?

The $hup$ gene is found in .........

Quite often,pulse crops are not manured with nitrogenous fertilizers. This is because: