The correct answer is A) tax law.
What is not part of the five departments headed by commissioners in a commission-style government is tax law.
One of the forms of local governments in America is the City Commission Government. One of its characteristics is that citizens can vote to elect commissions that constitute the legislative body in their place. This form of government combines aspects of the executive and legislative branch in order to better operate the city. What is not part of the five departments headed by commissioners in a commission-style government is tax law.