Petrified wood found in the middle of a lake most likely means that the area has not changed since the past
O was once a forest
once had a tropical climate
has always been a lake

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