Answer:
deadly force.
Explanation:
The United States Armed Forces defines deadly force as force a person or police officer uses with the intention of causing serious harm, injury or even death. Police officers are permitted to use deadly force when it reasonably apparent that a person is posing serious threat and harm to either themselves or other individuals. In this instance, since Johnny is charging at the police officer with a knife and the intention to kill him, the officer may use deadly force to stop Johnny.