What causes a solution to a rational equation to be an extraneous solution? When there is more than one solution, one of the solutions is extraneous. If a solution results in zero when substituted into the denominator of the equation, the solution is extraneous. If a solution results in a negative number when substituted into the denominator of the equation, the solution is extraneous. When a solution is a fraction, the solution is extraneous.

- A rational equation is an equation that involves fractions with polynomials in the numerator and denominator. - An extraneous solution is a solution that is obtained during the solving process but does not satisfy the original equation. - The key issue in rational equations is division by zero. For instance, if we have the rational expression \[ \frac{P(x)}{Q(x)}, \] then \( Q(x) \) must not be zero. - If substituting a candidate solution into \( Q(x) \) results in \[ Q(x) = 0, \] that candidate must be discarded because it would make the original expression undefined. - Therefore, the correct statement is: **If a solution results in zero when substituted into the denominator of the equation, the solution is extraneous.**