Which of the following statements is TRUE? a. One of the main advantages of cluster sampling over simple random sampling is its greater statistical efficiency for the same size sample. b. In cluster sampling, the parent population is broken into mutually exclusive and exhaustive sub-groups and a simple random sample is selected from each subgroup. c. In order to yield high statistical efficiency, each cluster in a cluster sample should include as many diverse universe values as possible. d. All of these statements are false. e. Cluster samples are most statistically efficient when the clusters are internally homogeneous.