Which of the following helps in coal formation?

Multiflagellate male gametes (sperms) are found in

In pteridophytes,the sporophytes consist of leaf-like appendages called

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.

In most of the pteridophytes,all the spores are of similar kind. Such plants are called ......

Selaginella has a character of evolutionary importance. That character is