Which of the following persons might be least apt to have age-related memory loss?

Which of the following persons might be least apt to have age-related memory loss?
 
  a. Alice, who at 78 is active in her church, still walks two miles a day, and has recently joined the Great Books Club, which meets regularly for literature discussions in her neighborhood
  b. Mary, who at 78 is widowed and is quite content to be alone
 c. Anita, who is 78, has never married, lives in a peaceful country home, and spends a great deal of time knitting and crocheting for charity
  d. Joanne, who is 78 and spends most of her time watching television game shows