Question: Rule I

Answer: A word root links to a suffix that begins with a vowel

Question: Rule II

Answer: A combining form (root + o) links to a suffix that begins with a consonant.

Ex: arth/o/centesis

Question: Rule III

Answer: A combining form (root + o) links a root to another root to form a compound word, even if the second root begins with a vowel.

Ex: oste/o/arthr/itis