Step 1: Understanding the Concept:
Chandigarh is a highly urbanized Union Territory.
Its agricultural area is extremely small, but it boasts near-complete irrigation coverage due to extensive urban tube-well systems and canal networks.
Step 2: Detailed Explanation:
Because of the minimal, flat agricultural land remaining in the periphery of Chandigarh, the available cultivated fields are fully supported by well-developed, modern irrigation systems.
Official agricultural statistics record that the net and gross irrigated area in Chandigarh reaches practically 100%.
Step 3: Final Answer:
The approximate irrigated area of Chandigarh (UT) is 100%, which is option (D).