Final answer:
The activity of non-violently gathering to support a cause in front of a property is best described as a peaceful demonstration, which is an important form of political participation and expression.
Step-by-step explanation:
The best way to describe the activity of a group of people who are sympathetic to a cause and have gathered in front of a property to voice their concerns without violence is A. Peaceful demonstration. This form of political participation allows people to call attention to a cause and express policy demands. Protests can be an important form of political participation across different types of societies, whether they are democratic, authoritarian, or experiencing social movements aimed at resistance or even revolution. Regulations around protests, such as the requirement for permits and free-speech zones, must be applied without discrimination to ensure fairness and uphold the rights to freedom of expression.