(c) : Parasitism is a relationship between two living organisms of different species in which one organism called parasite obtains its food directly from another living organism called host. The parasite spends a part or whole of its life either on or inside the body of the host.

The general parasitic adaptations are $(i)$ anaerobic respiration in internal parasites, $(ii) $ loss of certain organs, $(iii)$ presence of adhesive organs, $(iv)$ excessive multiplication, $(v)$ resistant cysts and eggs for safe transfer of their progeny to new hosts and $(vi)$ well developed and complicated reproductive organs.