Which of the Following Is an Example of Excessive Force

Which of the following is an example of excessive force used by a police officer?

A) A compliance hold on a subject who is physically fighting with his wife during a domestic disturbance
B) Placing a firearm against the head of an armed suspect who holds a knife,just stabbed a store clerk,won't put the knife down,and is yelling that he is going to kill the officer
C) Taser on a middle-school student (12 years old) who spits at the police officer
D) All of the above are examples of excessive force.