What would be the best advice to give someone who wants to retain good cognitive functioning as long as possible in old age?

The correct answer is Exercise your body and your mind.  For one to retain good cognitive functioning as long as possible, it is important that they use their senses or else risk losing them. This is because the fitness that comes with exercise results in fewer age-related changes in the brain.

Write out a reference sheet. document your findings. use a presentation to show the findings. give a detailed outline to each individual.