The correct answer is (b), Eran inscription.
The Eran inscription is a rock-cut edict of the Gupta king Samudragupta, dated to the 4th century CE. It is one of the earliest inscriptions to mention the practice of sati, or widow burning. The inscription states that Samudragupta’s father, Chandragupta I, had ordered that all widows of his soldiers who died in battle should be burned on their husbands’ funeral pyres. This practice was seen as a way to honor the dead and to ensure their safe passage to the afterlife.
The other options are incorrect. The Prayag Prashasti is an inscription of the Gupta king Ashoka, dated to the 3rd century BCE. It does not mention the practice of sati. The Junagarh inscription is an inscription of the Western Kshatrapa king Rudradaman I, dated to the 2nd century CE. It does not mention the practice of sati. The Ajanta inscription is a Buddhist cave inscription, dated to the 6th century CE. It does not mention the practice of sati.
The practice of sati was outlawed in India in 1829. However, it continues to be practiced in some parts of the country, despite the law.