With reference to the drainage system in Harappan cities which of the following statement is incorrect?
1
The drainage system in Harappan cities indicates the town planning.
2
Every house was supposed to have at least one wall along a street to allow the domestic wastewater to flow out in the street drains.
3
The main drain was covered by brick slabs or corbelled brick arches.
4
Underground drainage at Mohenjodaro is the most unique.