Heavy trailers or semi-trailers are those with a maximum authorised mass …

A)equal to 750 kg.
B)not exceeding 750 kg.
C)exceeding 750 kg.Correct
Trailers are classified as: - Light: up to 750 kg MAM (maximum authorised mass). - Heavy: more than 750 kg MAM (maximum authorised mass). With a category B licence, you may tow a light trailer without needing any additional licence.