"In competition-fostering situations, individuals act more competitively than do groups" is not true of competition.
Answer: Option D
Explanation:
When a group becomes competitive the collective actions of the individuals of the group tends to intensify and becomes a large competitive force. In that case, it obviously becomes more than the competitive spirit of an individual.
In this case, the competitive spirit of an individual does not become relevant but it is rather buried under the collective identity of the group. So, competition arise when a person thinks the limited ability than others and creates a deep disagreement also. Hence, option D seems to be not true about competition.