For a rational number to generate a repeating decimal, the correct statement is:
The denominator must not evenly divide any power of 10.
This means that for a fraction in its simplest form, if the only prime factors of the denominator are 2 and/or 5, it will result in a terminating decimal. However, if the denominator has prime factors other than 2 and 5 (for example, 3 or 7), then the decimal representation will be repeating.