Final answer:
The nurse should assess a toddler's ability to throw a ball overhand without losing balance at the 24-month health maintenance visit, as this is when such motor skills are typically developing.
Step-by-step explanation:
The nurse should assess the ability to throw a ball overhand without losing balance during the health maintenance visit for a toddler-age client at 24 months of age. By 18 months, children begin to master the ability to play with a ball by rolling or tossing it, but more complex motor skills, such as throwing a ball overhand without losing balance, typically develop as they approach two years of age. At 24 months, toddlers often show enhanced motor skills including the ability to run and potentially throw without losing balance, making this the appropriate age for the nurse to assess this particular skill.