When Maegasthense visited India he found that

Megasthenes, the Seleucid envoy at the Mauryan court in the late fourth century BCE, is quoted by Strabo and Arrian as saying that in India no one is a slave. That is the core point. Among the options, D is the one that fits the Indian legal picture of the period. The Arthashastra of Kautilya lays down penalties for a master who violates the chastity of a female slave, so the protection of slave women was a matter of law.

• A is wrong: Greek accounts describe Indian society as having no slaves in the Greek sense, so an open slave market is not something Megasthenes reported.
• B is wrong: Sale of free-born children into slavery was prohibited. Arrian records that Indians did not use slaves at all, and the Arthashastra treats free Aryans as non-enslaveable.
• C is wrong: It has no basis in the sources. Slaves were not barred from earning on their own in the way the option suggests.

The question sits in the Mauryan-period source material you need for Ancient India and for Mains questions on labour, social organisation and the Arthashastra as a source. A caution: Megasthenes' own statement is an absolute claim that no Indian was a slave, so the question is loosely framed and D is the best-supported option rather than a verbatim quotation.

Trap: candidates pick A because it sounds like a description of slavery, when the source tradition is precisely that Indians were not enslaved in the Greek manner.