Answer: The most effective thesis statement for this topic is B. Some benefits of playing football include being healthy, working with a team, and having a competitive energy.
Explanation: Sentence B. can function as an effective thesis because it makes reference to the different benefits that playing football can bring about, such as being healthy, working with a team and having a competetitive energy. In that way, unlike sentences A. and C., sentence B includes more than one benefit. Moreover, sentence D. does not refer to benefits strictly since it considers "fighting against others" as one of them. On the other hand, sentence B. presents actual benefits that can also be supported with evidence.