Which of the following is absent in plants?

Arrange the following in the correct sequence in the evolution of the nervous system:
$(a)$ Formation of a centralised nervous system.
$(b)$ Diffused nervous system in $Hydra$.
$(c)$ Formation of a ganglion.
$(d)$ Nervous system is lacking in sponges.

Neural coordination is

Which of the following systems provides the fastest means of communication within the body?

In Hydra,neural organization is comprised of:

What are the main functions of the neural system?