A survey was conducted in a large city concerning the reading ability of students in grade 5. To conduct the survey, researchers obtained a sample of students and administered a standardized test of reading ability to the selected students. The researchers selected a random sample of four school divisions within the city; they then picked a random sample of three elementary schools within each of the selected school divisions. Since there were many grade 5 classes in each of these selected schools, a further sample of one class from each school was picked at random and all the students in that selected class were given the reading test.

The sample of students was selected using which type of sample design?

a. A simple random sample (SRS) design.
b. A stratified random sample design with an SRS from each stratum.
c. A systematic random sample design.
d. A volunteer sample design of students
e. A multistage sample design.