Which of the following is/are a feature of Harappan sites after the decline of Mature Harappan culture?

All of the above

Features of the Harappan sites after the decline of Mature Harappan culture:

Abandonment of Mature Harappan sites:  By around 1800 BCE, most of the Mature Harappan sites, particularly in regions like Cholistan, were abandoned. This indicates a significant decline in population and activity in these areas.
Expansion into new settlements: At the same time, there was a population expansion into new settlements in regions such as Gujarat, Haryana, and western Uttar Pradesh.
Transformation of material culture: In the few Harappan sites that continued to be occupied after 1900 BCE, there was a noticeable transformation in material culture. Distinctive artefacts of the civilization, including weights, seals, and special beads, disappeared. Writing, long-distance trade, and craft specialization also declined.
Decreased production and construction: Overall, there was a decline in the production of artefacts, as fewer materials were used to make fewer things. House construction techniques deteriorated, and large public structures were no longer produced. This suggests a shift towards a more rural way of life.

End of a unifying element: It is believed that a strong unifying element, possibly the Harappan state, came to an end. This is evident from the disappearance of seals, script, distinctive beads, and pottery. There was also a shift from a standardized weight system to the use of local weights. The decline and abandonment of cities further support the idea of the collapse of the Harappan state.