Study the following statement and identify how many are true for lichens:
  (a) The association in lichen is sometimes considered as Helotism.
  (b) They are pioneer species in hydrosere 
  (c) There is no mention of lichens in Whittaker’s classification
 

Lichen thalli were considered to represent a consortium between the algae and fungi. Its association is sometimes considered as Helotism - a relationship which is often referred to as ‘Master- Slave’ relationship. Fungus lives as a dominant organism and algae like a slave. 
In the five-kingdom classification of Whittaker there is no mention of lichens and some acellular organisms like viruses, viroids and prions.
Lichens are of tremendous ecological importance as they are pioneers of  lithosere (succession on barren rocks). Phytoplanktons act as pioneer species in hydrosere.