Answer:
A. Lawsuit
Explanation:
A lawsuit can be defined as a dispute or claim brought by an individual or group of people (party) against another to a court of competent jurisdiction for the singular purpose of adjudication.
Hence, a civil lawsuit in which a large group sues is known as a lawsuit. The processes involved in the civil lawsuit is generally referred to as a litigation.
For example, a community comprising of a large group of people may file a civil lawsuit in the court of law against a company causing air pollution in their community.