Which country control the opium trade prior to the opium wars?

Which of the following contributed most to making the items listed in the box

Countries that are neither core nations nor peripheral nations

Donald is studying the eating habits of all students attending his school. he samples the population by dividing the students into groups by grade level and randomly selecting a proportionate number of students from each group. he then collects data from the sample. which type of sampling is used? select the correct answer below: systematic sampling convenience sampling stratified sampling cluster sampling