Final answer:
The best inequality to represent Alejandra having read less than 16 books this year is D. x < 16. This indicates that the number of books she has read is less than the given number.
Step-by-step explanation:
To represent Alejandra's situation of having read less than 16 books this year, we need to select the inequality that correctly showcases this condition. The symbol '<' is used to depict 'less than', which means the correct inequality would be one where the number of books she has read, represented by 'x', is less than 16.
Therefore, the inequality that best represents Alejandra's situation is D. x < 16. This inequality states that the number of books Alejandra has read is less than 16. Inequality symbols can sometimes be confusing, but remember that '<' looks like an 'L' for 'less than', which can help you remember that it represents a value smaller than the one it's compared to.