A research team is studying the effects of specific forms of therapy in treating anxiety. In the study, participants in Group 1 are brought into the lab to fill in some questionnaires and have their anxiety assessed but are not given any therapy, Participants in Group 2 are given therapy A, Participants in Group 3 are given therapy B, Participants in Group 4 are given a combination of both therapy A and therapy B, Afterwards the participants from all four groups are assessed for their anxiety and it is found that participants in groups 1-3 all experienced a reduction in their anxiety levels, but participants in group 4 did not experience any improvement in their anxiety Which group experienced the placebo effect?

A- none of the group experienced a placebo effects
B- group 2
C- group 4
D-group 3
E- group 1