During Pleistocene epoch, four glacial phases were identified. Which one of the following is the correct chronological order in which they appeared during this epoch from early times?

• A. Gunz - Mindel - Wurm - Riss
• B. Gunz - Mindel - Riss - Wurm
• C. Wurm - Riss - Mindel - Gunz
• D. Mindel - Gunz - Riss - Wurm