Answer: (d)

Explanation:
Statement 1 is correct: The mathematical concept of the decimal place-value system was adapted gradually into Indian epigraphy. The Mankani copper plates from Gujarat, dated accurately to AD 595–596, are widely recognized by historians and epigraphists as the earliest confirmed epigraphic evidence utilizing the decimal place-value system in India.

Statement 2 is correct: While early inscriptions occasionally relied on older numerical systems, the ninth century marked the historical threshold where the modern place-value notation became widespread and general in stone and copper plate inscriptions all over the Indian subcontinent.

Statement 3 is correct: Due to thriving maritime trade networks and robust cultural exchanges, Indian mathematical concepts traveled to Southeast Asia very early. This transmission is proved by Sanskrit inscriptions found in Cambodia and Indonesia dating as early as the seventh century (such as the Sambor inscription of AD 683), which clearly record dates using the Indian decimal place-value system.