Electronic opposition is the various activities performed to prevent enemy or hostile electronic countermeasures from affecting the combat effectiveness of host equipment and personnel, so as to protect the host's combat power from damage. The main measures include electronic counter-scouting, Electronic anti-interference, anti-radiation destruction, anti-directional blinding and computer virus infection. According to the definition above, Which of the following options do not involve electronic opposition:. ['Before the military exercise, the exercise command center conducts virus killing on the computers used in advance.', 'The launch vehicle launches anti-radiation missiles at the enemy and shuts down its electronic equipment to avoid accidental strikes.', 'Warships reduce the power of radar transmitting signals and set anti-radiation decoys in conflict areas.', "In order to counter the enemy's electronic interference, the headquarters decided to issue important instructions by a fixed telephone."]