Final answer:
The most important factor in a client learning new dietary habits for heart failure is their involvement in planning the dietary changes, which fosters ownership and adherence to the new guidelines.
Step-by-step explanation:
The most important factor in determining the client's ability to learn new dietary habits when reducing daily intake of sodium for heart failure is A. Involvement of client in planning the change. Engaging the client in the decision-making process is crucial as it encourages them to take ownership of their health, understand the need for change, and adhere to the new dietary guidelines.
Additionally, providing a balanced diet and education on nutrient and energy density can help in making healthier food choices. This involves de-emphasizing processed foods, which are often high in sodium, in favor of whole foods that are naturally lower in sodium and healthier fats.