Which one of the following construction techniques was most probably not known or widely used by the people of the Harappan or Indus Valley civilisation?

Introduction / Context:
The Harappan or Indus Valley civilisation is known for its advanced urban planning, use of baked bricks, and drainage systems. However, there were still some architectural features that developed only in later historical periods. This question asks you to identify which construction technique does not belong to Harappan architectural practice, an important detail for ancient Indian history exams.

Given Data / Assumptions:

• The focus is on the Harappan or Indus Valley civilisation.
• Several construction related practices are listed as options.
• Only one technique was not known or not widely used by Harappans.

Concept / Approach:
Archaeological evidence shows that Harappans built brick lined wells, well planned drainage systems, and multi room houses with flat roofs. They also used platforms and basic column like supports. However, the use of true arches for large openings, which require precise keystone technology, becomes clearly visible in later architectural traditions. Therefore, the absence of true arches is a recognised feature in Harappan architecture.

Step-by-Step Solution:
Step 1: Recall that Harappan cities like Mohenjodaro and Harappa had numerous brick lined wells. Step 2: Remember the famous covered drains that ran along streets, showing their expertise in drainage. Step 3: Note that residential buildings used baked bricks and mostly flat roofs supported by simple structural elements. Step 4: Understand that true arches, with wedge shaped stones and a keystone at the top, emerged in later architectural history. Step 5: Conclude that construction of true arches is the technique not associated with Harappans.

Verification / Alternative check:
Any standard archaeology text on the Indus Valley civilisation lists features such as wells, bathrooms, drainage lines, and brick platforms but does not mention true stone arches. In fact, the appearance of arches is often associated with later periods including certain Buddhist and Islamic architectural forms in the subcontinent.

Why Other Options Are Wrong:
Option A is wrong as a choice because brick lined wells are well documented at Harappan sites. Option B is also wrong because platforms and simple pillars occur in many excavations. Option C is wrong because Harappans are famous for their advanced drainage system. Option E is wrong since baked brick houses are one of the hallmarks of Harappan urbanism.

Common Pitfalls:
Some learners may confuse the absence of arches with other advanced features and mistakenly think that drains or wells were not present. Another pitfall is not distinguishing between simple openings and true keystone arches. Always remember that drains, wells, and brick houses are strongly associated with Harappans, whereas true arches are not.

Final Answer:
The construction technique not known or widely used by the Harappans was the construction of true arches for large gateways and openings.