Desmond and lucy, both in their mid-50s, wish to maintain their excellent brain functioning into their 70s, 80s, and even beyond. the best way to accomplish their goal is to:

Maintain good general health.

Explanation:

General health is defined as state of well being with proper mental and physical functioning of the body. Good general health keeps the body and mind happy , properly functioned body parts ,immunity to fight against disease and other illness,etc.

According to the situation of the question, Desmond and Lucy should be try to maintain their general health so that mind and body can stay at stable state of well being.In this way they will be able to maintain their functions of brain in future.

1. seasonal

2. frictional unenployment

3. the number of the labor force multiplied by 100 and then subtract the number of unemployed.

4. 4%

5. an increase in prices