Choose exactly two appropriate reasons below to go in the place of ______and_________.
a) Genetics may affect the way coffee affects an individual, make it more or less appealing.
b) People can get used to caffeine and require more of it to stay awake.
c) Genetic factors may affect how much sleep you get.
d) Depression goes un-diagnosed in many people.
e) People may not want to admit they are depressed in a survey.