For Questions Use the Following Narrative

Multiple Choice

For Questions use the following narrative
Narrative: Apartment complex
Suppose you want to survey the opinions of the residents of an apartment complex.The complex contains 100 buildings, each with 8 units per building, for a total of 800 units.You decide to sample 160 of the units.
-{Apartment complex narrative} Suppose 50 of the buildings (400 total units) are for singles, and 50 buildings (400 units) are for non-singles.You randomly select 80 single units and then you randomly select 80 non-single units.What sampling method did you use?

A) A systematic sample.
B) A stratified sample.
C) A cluster sample.
D) A simple random sample