Final answer:
The correct simplified algebraic expression is D. (x - 5) / 5 + 10, because the constant 10 does not combine with the fraction, as it is not under the division.
Step-by-step explanation:
The simplified algebraic expression of (x - 5) / 5 + 10 is determined by identifying that the addition of 10 does not combine directly with the fraction (x - 5) / 5, and it stands separate from it. Therefore, the expression remains unchanged when simplified, and the correct choice is D. (x - 5) / 5 plus the separate constant 10. This is because the 10 is not under the division by 5, so it cannot combine with the (x - 5) term which is being divided by 5.