Which of the following is the most stable ecosystem?

Ocean is the answer. Stability here means the ecosystem resists sharp changes in its physical conditions and recovers slowly from disturbance. The ocean is vast, so its temperature, salinity and light levels change very little over time and across space, and its huge volume buffers the effect of local disturbances.

• Desert: Extreme daily and seasonal temperature swings, scarce water and low productivity make it fragile with little buffering capacity.
• Mountain: Altitude-linked changes in temperature, oxygen, soil depth and slope make conditions patchy, and erosion and landslides disturb it easily.
• Forest: Fairly stable and diverse, but terrestrial forests are exposed to fire, drought, cyclones and clearing, and their conditions vary far more than ocean waters.

Core concept: ecological stability has two parts, resistance and resilience, and environmental buffering is central to both. Mains link: this is why coral reef and mangrove degradation and ocean warming matter for climate policy and blue economy questions.

Trap: Aspirants pick Forest because it is rich in species diversity. Diversity is one factor, but this question asks about physical stability, where the ocean's uniform conditions win.