Final answer:
Option A) Place a towel roll under the client's neck or shoulder during the acute phase.
Step-by-step explanation:
To prevent contractures associated with a deep partial-thickness injury to the posterior neck, the nurse should use option A) Place a towel roll under the client's neck or shoulder during the acute phase. This intervention helps to maintain proper alignment and prevents the neck from flexing forward, reducing the risk of contractures. It provides support and helps to maintain the natural curvature of the neck.