Consider the following statements:

1. At Kalibangan, the lower town was fortified.

2. At Lothal, 'citadel' and 'lower town' were integrated to fall within a common fortification wall.

3. At Surkotada, 'citadel', and 'lower town' were conjoined and both were fortified.

4. No fortification excavated around the 'lower town' in Mohenjo Daro.

Select the correct answer from the following options: