Trabeculae in $Selaginella$ stem represent

$Pteris$ and $Adiantum$ resemble each other in having:

Which of the following statements is correct?

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.

The development of the sporangium in $Dryopteris$ is:

Sporangia and spore-bearing leaves in ferns are called: