Which of the following breaker sizes would most likely be used for lighting circuits?

The use of a 20 amp breaker for lighting circuits is standard because it aligns with the National Electrical Code (NEC) guidelines. Lighting circuits typically do not require high current levels, as the lighting fixtures and associated load are generally designed to operate within the 15 to 20 amp range.

A 20 amp breaker provides adequate capacity for the number of light fixtures and their wattage that are often connected to a typical lighting circuit without risking overload. In residential settings, it's common for circuits designated for general lighting or receptacles to utilize a 15 amp or 20 amp breaker, with 20 amps being more prevalent for overhead lighting where multiple fixtures may be in use.

Higher amperage breakers, such as 30, 40, or 60 amps, are generally used for larger appliances or specific high-load applications, such as electric ranges, water heaters, or various types of machinery. Using such high-capacity breakers for lighting could potentially create a safety hazard, as they may allow too much current to flow without tripping, leading to overheating and increased fire risk in wiring that is not designed to handle those higher loads.