What is the definition of the informal market?

I - It is a market where the exchange of goods or services between economic agents is carried out without submission to the rules that regulate commercial exchange, production or the provision of services.
II - It is a sector of the economy that operates outside the established legal or institutional framework.
III - It is a market that is generated mainly in developed countries due to excess labor supply.
a) Only I is correct.
b) Only II is correct.
c) I and II are correct.
d) II and III are correct.