What is the main source of Spanish mercantile law?

I - The Spanish Constitution of 1978 contains the principles, fundamental rights and duties in economic matters.
II - The Spanish Commercial Code of August 22, 1885 is the main source of mercantile law.
III - The European Union's original law is made up of the constituent Treaties of the European Communities.
IV - The European Union's derived law is made up of regulations and directives that harmonize the legislation of the member states.
a) I and II are correct.
b) II and III are correct.
c) III and IV are correct.
d) I and IV are correct.