A _____ year old electrical breaker is generally considered to be at its life expectancy.

An electrical breaker typically has a life expectancy around 30 years, which is why this choice is considered correct. Over time, the mechanical and electrical stresses on the breaker can lead to wear and tear, making it less reliable. Breakers may continue to function beyond this age, but their performance can be unpredictable, and they may not trip as effectively under fault conditions.

While options such as 20, 25, and 35 may reflect different component lifespans in certain scenarios, they generally do not match the standard life expectancy of residential electrical breakers. Breakers approaching or exceeding 30 years of service should be assessed for condition, and replacement is often advisable to ensure optimal safety and reliability in electrical systems.