The most common form of official violence is

A) police brutality against citizens.
B) the exposure of average citizens to dangerous chemicals.
C) strictly enforcing the tax laws.
D) the adding of experimental birth control liquids into the rations of Army soldiers.

Police brutality against citizens is the most common form of official violence, where law enforcement officers use excessive force and act outside the law while performing their duties. This issue has been a serious concern in many countries, leading to protests, calls for police reform, and increased scrutiny and accountability for law enforcement agencies. The other options listed do not reflect common forms of official violence.