The correct answer is - c. command.
North Korea is a country where the government is controlling everything in the country, natural resources, media, production facilities, agricultural land...
The country is functioning on the basis and ideologies of the communism since it was formed, and it seems that it will stay that way for the foreseeable future.
Since the government is controlling the economy, and it is in the way of self-sustainability, so the economy is of the command type.