Ph.D. candidates undertaking research must typically complete a thesis, or dissertation, consisting of original research representing a significant contribution to their field, and ranging from two-hundred to five-hundred pages. Most Ph.D. candidates will be required to sit comprehensive examinations—examinations testing general knowledge in their field of specialization—in their second or third year as a prerequisite to continuing their studies, and must defend their thesis as a final requirement. Some faculties require candidates to earn sufficient credits in a third or fourth foreign language; for example, most candidates in modern Japanese topics must demonstrate ability in English, Japanese, and Mandarin, while candidates in pre-modern Japanese topics must demonstrate ability in English, Japanese, Classical Chinese, and Classical Japanese.