The regulated market have been established by:

Correct option is C

State governments are responsible for establishing regulated markets under the Agricultural Produce Market Committees (APMC) Act. These markets aim to provide farmers a platform for transparent pricing, reducing exploitation by intermediaries.
Explanation of other options:
(a) District Municipal Corporation: They are responsible for urban governance and do not regulate agricultural markets.
(b) Panchayats: Local governance bodies focus on rural development but do not manage regulated markets.
(d) Central government: While it provides policy guidance, the execution and establishment of markets lie with state governments.