To achieve consistent amounts of restorative sleep, what is the best process to follow?

Select one:

a$.$ Begin a routine of random bedtime and risetimes to develop resistance to disruptions in sleep patterns.

b$.$ Begin a routine of no heavy exercise at least $3$ hours before bedtime in order to ensure proper sleep and body rhythm$.$

c$.$ Begin a routine for bedtime and risetime that varies by no more than $1$ hour to help develop a daily body rhythm$.$

d$.$ Begin a routine of consuming no heavy foods or caffeine at least $2$ hours before bedtime in order to stimulate REM sleep.