1) Which of the following is a correct statement about clustered and stratified survey designs? [1 mark] A. The sampling unit and observation unit are different things (i.e., different elements) in both clustered and stratified survey designs. B. The strata in stratified designs are sampled at random, whereas the clusters is clustered designs are defined ahead of time. C. Clustered and stratified surveys are two names for the same survey design. D. There is no randomness in a stratified survey design, whereas there is randomness in a clustered survey design. E. Clusters are randomly selected in clustered surveys, whereas strata are not in stratified surveys