An ad hoc committee is a committee formed:

An ad hoc committee is indeed formed for a special purpose. This type of committee is typically established to address a specific issue or task that arises, and it is usually temporary in nature. Once the purpose has been achieved or the task is completed, the ad hoc committee is disbanded. This flexibility allows organizations to respond quickly to particular needs without creating a permanent committee structure.

In the context of other options, a committee formed for dispute resolution may have a specific function but does not encompass the broader range of purposes that an ad hoc committee can serve. Summarily implies a process that is abrupt or hasty, which is not a defining characteristic of ad hoc committees. Retrospectively suggests looking back at past events, which does not align with the forward-looking, problem-solving nature of an ad hoc committee’s function. Therefore, the focus on special purpose makes the correct choice clear.