The correct answer is 1, 2, and 3 only.

• It is a planned settlement that is divided into two sections, one smaller but higher (Citadel) and the other much larger but lower (Lower Town).
• The Citadel owes its height to the fact that buildings were constructed on mud-brick platforms.
  • It was walled, which meant that it was physically separated from the Lower Town.
  • It had structures that were probably used for special public purposes.
• The Lower Town was also walled. Several buildings were built on platforms, which served as foundations. Hence, Statement 1 is correct.
• Signs of planning: bricks, which, whether sun-dried or baked, were of a standardized ratio, where the length and breadth were four times and twice the height respectively.
• The most distinctive feature of Harappan cities was the carefully planned drainage system.
  • The roads and streets were laid out along an approximate “grid” pattern, intersecting at right angles. Hence, Statement 2 is correct.
  • It seems that streets with drains were laid out first and then houses were built along with them.
• ​The Lower Town at Mohenjodaro provides examples of residential buildings.
  • The courtyard was probably the center of activities such as cooking and weaving, particularly during hot and dry weather.
  • There are no windows in the walls along with the ground level.
  • The main entrance does not give a direct view of the interior of the courtyard.
  • Every house had its own bathroom paved with bricks, with drains connected through the wall to the street drains. Hence, Statement 3 is correct.
  • Some houses have remains of staircases to reach a second story or the roof. Hence, Statement 4 is incorrect.
  • Many houses had wells, often in a room that could be reached from the outside and perhaps used by passers-by. 
• The citadel includes the warehouse: a massive structure of which the lower brick portions remain, while the upper portions, probably of wood, decayed long ago and the Great Bath.