Researchers are studying the use of urgent care centers within a county. They suspect use of urgent care centers is less common in rural areas because they are not as conveniently located to most of the population . The county has a population of 200,000 people, with 20 % residing in urban areas . The researchers decide to survey 1000 urban individuals (out of 40,000 in urban areas, to give a 1 in 40 sample.) 2000 rural individuals are included , out of 160,000, resulting in a 1 in 80 sample . Which of the following methods of sampling does this represent ? A. Stratified sampling B. Cluster sampling . Systematic sampling . Simple random sampling