A positive integer is called tidy if and only if all of its digits, written in base , are different from one another. For example and are tidy, but and are not.
Which one of the following statements is not true?
AEvery one-digit positive integer is tidy.
BThe sum of two tidy numbers is always tidy.
CThere are only finitely many tidy numbers.
DEvery tidy number has at most digits.