I. p only if q. This says that number is a multiple of 9 only, if it is a multiple of 3. II. q is a necessary condition for p. This says that when a number is a multiple of 9 , it is necessarily a multiple of 3 . III. ∼q implies ∼p. This says that if a number is not a multiple of 3 , then it is not a multiple of 9 .