Final answer:
The expression |9y - z| represents the non-negative value of 9y minus z and cannot be simplified to any of the given options without additional context.
Step-by-step explanation:
The absolute value function, denoted by |x|, takes any number x and returns its non-negative value. When considering the expression |9y - z|, the absolute value function does not simplify the variables themselves but rather ensures the result is non-negative. Therefore, the answer to the question |9y - z| cannot be simplified to any of the options (A) y - z, (B) z - y, (C) 9y - z, or (D) z - 9y directly because these options do not include the absolute value signs. The expression within the absolute value |9y - z| simply implies the non-negative distance of 9y from z on the number line, but does not resolve to a specific algebraic form without additional context or specific values for y and z.