Which of these statements best defines a stratified random sample?

• a.)It is a sample where every nth element of the population is selected in a sequence.
• b.) It is a sample where the population is first broken into homogenous groups and then elements are randomly selected, in proportion, from each group.
• c.) It is a sample where the population is divided into roughly equal groups, and then elements are randomly selected from each group.
• d.) It is a sample in which every element has the same chance of being selected from the total population.