Correct Answer: C
Explanation:
The original text contains a pronoun agreement error. The possessive pronoun "their" is plural, but it is intended to refer to the singular noun "individual." We must use singular possessive pronouns instead, such as "his or her."
Only answer choices "depends on his or her weight, height, and how old they are" and "depends on his or her weight, height, and age" correctly use "his or her" instead of "their," but answer choice "depends on his or her weight, height, and how old they are" does not use correct parallel structure. Therefore, the answer choice "depends on his or her weight, height, and age" is correct.