Official Journal of the European Union
2042/2003 ANNEX III
(Part-66)
Para 5 answers your question,
3. for category C with respect to large aircraft:
(i) three years of experience exercising category B1.1, B1.3 or B2 privileges on large aircraft or as Part-145 B1.1, B1.3 or B2 support staff, or, a combination of both; or
(ii) five years of experience exercising category B1.2 or B1.4 privileges on large aircraft or as Part-145 B1.2 or B1.4 support staff, or a combination of both; or
4. for category C with respect to non large aircraft:
three years of experience exercising category B1 or B.2 privileges on non large aircraft or as Part-145 B1 or B.2 support staff, or a combination of both; or
5. for category C obtained through the academic route:
an applicant holding an academic degree in a technical discipline, from a university or other higher educational institution recognised by the competent authority, three years of experience working in a civil aircraft maintenance environment on a representative selection of tasks directly associated with aircraft maintenance including six months of observation of base maintenance tasks.
But one would hope if you were educated/keen enough you would have sought this information out - it is free on the web and a pre requisite for a C licence. (Pt 66 Module 10)