Q.Lichens are association of:

Lichens are a classic example of mutualism, not commensalism — but the question is about their composition. The NCERT textbook clearly states that a lichen is a symbiotic association between a fungus (the mycobiont) and an alga (the phycobiont). The fungus provides shelter and absorbs water and minerals, while the alga performs photosynthesis to produce food. This is a mutually beneficial relationship, not a one-sided commensal one.

• The fungal partner is usually an ascomycete.
• The algal partner is typically a green alga or a cyanobacterium.
• The association is so intimate that lichens are often named as separate organisms. …

Lichens are one of the most striking examples of mutualism in nature — a partnership so intimate that the two organisms merge into a single, stable body called a thallus. The NCERT textbook for Class 11 Biology (Chapter 2, Biological Classification) clearly states that lichens consist of a fungus (the mycobiont) and an alga (the phycobiont). In some cases, the algal partner may be a cyanobacterium (blue-green alga), but the key point is that the association is always between a fungus and a photosynthetic partner.

The fungus provides the structure, anchorage, and protection, while the alga carries out photosynthesis, supplying food. This is not a parasitic or competitive relationship — both partners benefit, which is why lichens can survive on bare rocks, tree bark, and in extreme climates where neither partner could live alone.

Now look at the options:

• (A) bacteria and fungus — Incorrect. Lichens do not involve typical bacteria as a partner. …

Recall the two named partners directly from the definition of a lichen (a specific fungus-alga, or fungus-cyanobacterium, pairing) rather than reasoning generally from the rules of m …