Answer: All boundary points of a rational inequality that are found by determining the values for which the denominator is equal to zero should always be represented by plotting an open circle on a number line.
Explanation:
Based on the options given in this question, it should be noted that the option that is true is that all boundary points of a rational inequality that are found by determining the values for which the denominator is equal to zero should always be represented by plotting an open circle on a number line.
Therefore, the correct option is A.