Final answer:
Writing letters to public officials is a conventional form of political participation.
Step-by-step explanation:
A conventional form of political participation is writing letters to public officials. This is a way for citizens to express their opinions and concerns to elected representatives and have their voices heard. Writing letters allows individuals to engage in the political process without physically protesting or boycotting products. While participating in a protest march, boycotting products, chanting slogans outside officials' windows, and staging a sit-in are all forms of political expression, they may be considered more unconventional or radical compared to conventional forms of political participation.