Degree regulations state that, to be awarded a degree, a student must have passed two honours examinations (i.e., two Tripos examinations) – this could include a Part I and a Part II, two Part I exams, or (in some cases) a Part I and a Part IA. From October 2011, students can only be awarded an honours degree if they have been awarded honours in a Part II or Part III examination; a combination of Part I examinations will allow a student to graduate with an Ordinary degree. All students must complete at least nine terms of residence (three years of study) – making it impossible for students to simply complete two one-year tripos parts. This makes it easy for an undergraduate to switch out of a subject. So a one-year Part I (or Part IA) must be followed by a two-year Part II, and usually vice versa. More exotic combinations are possible, with the permission of the student's college and prospective department, but some combinations create a four-year bachelor's degree. A few subjects – e.g. Management Studies, and Linguistics (prior to October 2010) – exist only as Part II, and can be preceded by any manner of Part I subject.