Which one is the most striking or common character of the vertebrates?

Elephantiasis is caused by

List out some common features in cat,rat and bat.

Classify organisms of kingdom $Protista$ on the following basis and give an example of each:
$(a)$ Based on structure for locomotion.
$(b)$ Based on mode of nutrition.

Associate the following features with appropriate organisms and their kingdom [in $(ii)$ and $(iv)$],division [in $(i)$] and phylum [in $(iii)$ and $(v)$].
$(i)$ Presence of pyrenoids
$(ii)$ Presence of heterocysts
$(iii)$ Presence of genital papillae and anus
$(iv)$ Presence of chloroplast and flagella
$(v)$ Presence of palp and parapodia

State reasons for the following:
$(a)$ Mammals have mammary glands.
$(b)$ Annelids have a true body cavity.
$(c)$ Fish possess gills.