Dr. Sheffield wants to investigate the causal relationship between frustration and memory. She divides participants into two groups using random assignment. One group is given a problem to solve that has no solution, inducing frustration, while the other group is given a problem to solve that has a solution. Then both groups have their memory tested. The group that is in the frustration condition can also be called the:______a. comparison groupb. control groupc. experimental groupd. posttest group