The correct answer is Manigrama. Here`s an explanation of all the options:

1) Chaturvedimangalam: This term refers to a particular type of village or habitation in ancient India, which was usually inhabited by the followers of the four Vedas, and was not a corporation of merchants.

2) Parishad: In ancient India, it referred to a type of assembly or council, often associated with governance or decision-making within a community or kingdom, not a merchants corporation.

3) Ashtadikgaja: This term has a mythical or religious connotation in ancient India. It refers to the eight elephants that, according to Hindu mythology, hold up the universe. This term has no direct connection with trade or merchants.

4) Manigrama: This was indeed a corporation of merchants in ancient India. Manigrama functioned like a guild, and was an organization of traders, often operating within a specific business or industry. They were quite prevalent in ancient India, facilitating commerce and trade.