When asked, "what makes things die? " a child responds, "you can die if you swallow a dirty bug." according to piaget's theory, this child is probably in which developmental stage?

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