For ag there is the core section and then there is a choice of the electives or the project. If you choose electives, after core tests you'll need to answer an extended response question on at least one elective (max of 2, depends how your school does it). After the HSC Core test, you need to answer 2 elective essay questions. While the electives do offer some information for the core, the elective marks are worth so much vis-a-vis that even small deductions screw you up. For example, at my school even poor projects (read: every project) recieved a mark of 25+, whereas in the electives 25+ was quite a decent mark.