What is a parallel study statistical study design? Group of answer choices a. A type of clinical trial in which all participants receive the same two or more treatments, but the order in which they receive them depends on the group to which they are randomly assigned. For example, one group is randomly assigned to receive drug A followed by drug B. b. A type of clinical study where two groups of treatments, A and B, are given so that one group receives only A while another group receives only B. c. Both a and b d. None of the above