Final answer:
The statement by the client that indicates adequate understanding of their diet restrictions is that they will mostly use salt substitutes for flavoring.
Step-by-step explanation:
The statement by the client that indicates adequate understanding of their diet restrictions is option c. "I will mostly use salt substitutes for flavoring."
This statement shows that the client understands the importance of limiting sodium intake, which is a key dietary restriction for individuals with hypertension. By using salt substitutes, the client can still add flavor to their food without increasing their sodium intake.