In the grasslands, trees do not replace the grasses as a part of an ecological succession because of

In the grasslands, trees do not replace the grasses as a part of an…

Answer

(a) insects and fungi: These are decomposers/herbivores and may affect vegetation locally, but they are not the main ecological reason grasslands remain grass-dominated. Verdict: Incorrect.
(b) limited sunlight and paucity of nutrients: Grasslands are generally open, well-lit ecosystems; lack of sunlight is not the limiting factor preventing tree replacement. Nutrient limitation alone is also not the standard explanation. Verdict: Incorrect.
(c) water limits and fire: Low/seasonal rainfall and recurrent fires prevent establishment of tree saplings and maintain grasses as the dominant vegetation in many grasslands. Verdict: Correct.
(d) None of the above: Since option (c) correctly explains the arrest of succession in grasslands, this is wrong. Verdict: Incorrect.