Vegetative reproduction in mosses takes place by .....

Calyptra develops from

The function of elaters is

Which one of the following is a true moss?

In the given figure of $Sphagnum$,what do $A$ and $B$ represent?

In mosses,the second gametophytic stage is the leafy stage. Consider the following statements about the leafy stage:
$I.$ The leafy stage is produced from the secondary protonema as a lateral bud.
$II.$ They consist of upright,slender axes bearing spirally arranged leaves.
$III.$ They are attached to the soil through multicellular rhizoids.
$IV.$ This leafy stage bears the sex organs.
Which of the statements given above are correct?