Answer:
<h2>There is a variable in the denominator of at least one involved fraction.</h2>
Step-by-step explanation:
The actual definition of a fractional equation could be:
In words, fractional equations are those which has variables in the denominator of a fractional term, that doesn't mean that all fractions must have a unknown denominator, but at least one of the denominators should have a variable.
Therefore, according to its definition, the right answer is third option.
<em>In addition, other options don't make sense, multiple variables is not necessarily the case for fractional equations. Similarly, not all denominators must have variables. And, having variable only in the numerators don't define the equation as fractional.</em>