Which one of the following scenarios illustrates a stratified random sampling procedure?
a. Putting all female participants' names into one hat, male participants' names - into another, and blindly drawing names from each hat separately.
b. Making a list of all potential participants, and choosing every third person on the list.
c. Putting all participants' names into a hat, and blindly drawing names from the hat.
d. Seating all participants around square tables, and choosing participants who sit facing North (one side of each table).