Which of the following statements best describes the benefits of research on the genetic bases of ...

Which of the following statements best describes the benefits of research on the genetic bases of memory?
 
  a. Presently available drugs show benefits in boosting human memory.
  b. Understanding the genetic bases of memory has led to development of drugs to boost memory in bothAlzheimer's patients and normal individuals.
 c. Scientists can prevent Alzheimer's disease in some cases through genetic manipulation of particular genes.
  d. Scientists have identified specific proteins regulated by so-called memory genes that can be synthesized to improve human memory.
  e. No drugs or supplements are yet available that have been shown to enhance memory in normal individuals.