A rational number can be described as a quotient of two integers, where the divisor (the denominator) is not zero. This means a rational number can be expressed in the form \( \frac{a}{b} \), where \( a \) and \( b \) are integers and \( b \neq 0 \). Therefore, the best response from your options would be:
"A rational number is a fraction that includes all integers except for when zero is the divisor."