Which of the following statements are not true regarding the randomized block design?

Which of the following statements are not true regarding the randomized block design?
 a. In this design, persons or test units are first arranged into similar groups, or blocks, then the treatments are randomly assigned.
  b. Blocking helps reduce error variation by ensuring that the treatment groups are comparable in terms of the blocking variable.
  c. This design assumes that interactions exist between the blocks and the treatments.
  d. Although the blocking variable can be viewed as representing a second independent variable, it is introduced solely for the purpose of controlling error variation.
  e. All of these statements are true.