Under what circumstances can a riot be declared?

A riot can be declared when two or more people gather unlawfully to disturb the peace because this scenario directly aligns with the legal definition of a riot. A riot typically involves a group of individuals engaging in violent or tumultuous behavior that disrupts public order and safety. The unlawful gathering aspect is crucial, as it indicates that the assembly does not have legal permission or purpose and is intent on causing unrest or chaos.

The other scenarios do not meet the criteria for declaring a riot. When people gather for a peaceful discussion, they are exercising their right to free speech and assembly without intending to disturb the peace. A noisy concert, while it may be disruptive, does not typically involve a group acting unlawfully with an intention to incite violence or chaos. Lastly, when a small group assembles for a lawful act, this is also a lawful gathering and does not represent the kind of behavior that would warrant a riot declaration. Thus, option B correctly identifies the conditions under which a riot can be declared.