Which one is used as a spice?

Correct answer: (b) Lichens

Explanation

Some lichens are used as spices. The best known is *Parmotrema perlatum*, called stone flower (patthar phool or kalpasi), which is used in garam masala and in Chettinad and Hyderabadi dishes for its earthy flavour.

A lichen is a partnership of a fungus and an alga (or a cyanobacterium). Fungi such as mushrooms are eaten as vegetables, but not as spices, and mosses and ferns are not used as spices.