Generally, you would offer three H2 content-based subjects and one H1 content-based subject. One of the four content-based subjects must be from a contrasting discipline. In addition, you would do General Paper (GP), Mother Tongue (MTL), and Project Work (PW) at the H1 level. 

Students who have done exceptionally well in the GCE O level Exams may also apply to do four H2 subjects, on top of GP, MTL, and PW at the H1 level. Check for details on the subject combination offered by SAJC here.