Martin Seligman Conducted Research Aimed at Finding Interventions That Are

Martin Seligman conducted research aimed at finding interventions that are effective as primary enhancements. He had four conditions: (1) the control group; (2) the gratitude group; (3) the three good things in life group, and; (4) the character strengths group. What did Seligman find?

A) Each of the treatments was effective in terms of raising the participants' happiness relative to the control group.
B) There were no differences in levels of happiness across the four groups.
C) Only the gratitude group showed a significant increase in participants' levels of happiness.
D) Only the character strengths group showed a significant increase in participants' levels of happiness.