A fraction is considered simplified when which condition holds?

1. A fraction can often be written in more than one equivalent form. 2. The simplest form is the one with the fewest common factors remaining. 3. A fraction is considered simplified if there are no common factors left in the numerator and denominator. 4. Being smaller than the denominator, having a prime denominator, or having equal numerator and denominator do not by themselves guarantee no shared factors remain. _Source: OpenStax Prealgebra (CC BY 4.0), Ch 4 "Fractions", section 4.2 Multiply and Divide Fractions_