Final answer:
The nurse should teach the parent to administer liquid iron preparations to the child with iron-deficiency anemia between meals.
Step-by-step explanation:
The nurse should teach the parent to administer liquid iron preparations to the child with iron-deficiency anemia between meals. This is because iron absorption is enhanced on an empty stomach. Administering iron with meals can decrease absorption due to the presence of other food components that can inhibit iron absorption. Therefore, administering iron between meals ensures optimal absorption.