Perched aquifers: identify the correct statements regarding occurrence, perched water table, and formation within an unconfined setting.

Introduction / Context:
Perched aquifers are local saturated zones situated above the regional water table due to intervening low-permeability layers. Recognizing perched conditions is essential for siting wells, assessing seepage, and interpreting soil moisture behavior.

Given Data / Assumptions:

• Unconfined setting with heterogeneous stratigraphy.
• Presence of a discontinuous impervious or semi-impervious lens (e.g., clay).
• Local recharge that can temporarily saturate the overlying zone.

Concept / Approach:
When infiltrating water encounters an intervening impervious lens above the regional phreatic surface, it can pond, creating a saturated zone with its own upper surface—the perched water table. This perched zone is hydraulically separated from the main water table and can be transient, depending on recharge and leakage.

Step-by-Step Solution:

Verification / Alternative check:
Hydrogeology references consistently define perched water tables and their formation over discontinuous lenses.

Why Other Options Are Wrong:

• Each individual statement (a)–(c) is correct on its own; selecting any single one would be incomplete.
• 'None of these' contradicts standard definitions.

Common Pitfalls:

• Confusing perched aquifers with truly confined aquifers.
• Assuming perched conditions are permanent; they are often seasonal or event-based.

Final Answer:
All the above