Which of the following statements is correct about the Harappan culture?

A- By c. 1800 BCE most of the Mature Harappan sites in regions such as Cholistan had been abandoned.
B- At the same time, there was an expansion of the population into new settlements in Gujarat, Haryana and western Uttar Pradesh.

Both statements are correct.

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.