Pteridophytes are classified into $4$ classes. Which of the following is $NOT$ one of them?

In $Dryopteris$ (fern),meiosis occurs during:

In pteridophytes,the main plant body is .........

The main plant body is differentiated into true root,stem,and leaves in:

The first evolution of the seed habit occurred in which of the following?

How many of the following statements are true about $Azolla$?
$(a)$ It is free-floating.
$(b)$ It has bilobed leaves.
$(c)$ It is nitrogen-fixing.
$(d)$ It is a climber.
$(e)$ It has Aerenchyma in the ventral lobe of the leaf.