Read the passage and answer the questions:
The most ancient system yet discovered

About the drains, Mackay noted: “It is certainly the most complete ancient system as yet discovered.” Every house was connected to the street drains. The main channels were made of bricks set in mortar and were covered with loose bricks that could be removed for cleaning. In some cases, limestone was used for the covers. House drains first emptied into a sump or cesspit into which solid matter settled while wastewater flowed out into the street drain. Very long drainage channels were provided at intervals with sumps for cleaning. It is a wonder of archaeology that “little heaps of materials, mostly sand, have frequently been found lying alongside drainage channels, which shows... that the debris was not always carted way when the drain was cleared”. Drainage systems were not unique to the larger cities but were found in smaller settlements as well, At lothal for example, while houses were built of mud bricks, drains were made of burnt bricks.

What was the material used for building the drainage channels in cities of Indus Valley Civilisation?

(1) Lapis Lazuli and Carnelian
(2) Bricks and mortar
(3) Stones and chalk
(4) Iron pipes

2

The material used for building the drainage channels in cities of the Indus Valley Civilization was Bricks and mortar.

About the drains, Mackay noted: “It is certainly the most complete ancient system as yet discovered.” Every house was connected to the street drains. The main channels were made of bricks set in mortar and were covered with loose bricks that could be removed for cleaning.