Electronic warfare (EW) encompasses actions against the enemy's use of the electromagnetic spectrum. Which of the following is a capability of EW?

• A. Electronic Support Measures (ESM) and electronic attack/jamming
• B. Cyber defense
• C. Navigation error correction
• D. Anti-submarine warfare sonar

Answer: (B)

EW focuses on actions against the enemy’s use of the electromagnetic spectrum. The best-fit capability here combines Electronic Support Measures, which listen for and identify enemy signals to provide intelligence and situational awareness, with electronic attack or jamming, which actively denies or degrades the enemy’s ability to use those emissions. Together, these illustrate direct EW activities: detecting and exploiting EMS while also restricting the adversary’s use of it. The remaining options belong to other domains—cyber defense pertains to cyberspace, navigation error correction relates to navigation systems rather than EMS, and sonar is an acoustic, not electromagnetic, capability used in anti-submarine warfare.