Final answer:
Candela (cd) is the correct unit for measuring the minimum light intensity detectable by the average human eye, as it is the standard unit of luminous intensity directly related to visual perception of brightness.
Step-by-step explanation:
The correct unit for measuring the minimum light intensity that an average human eye can detect is Candela (cd). Candela is the standard unit of luminous intensity, and it gives an approximation of the luminous intensity of common candles. It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540×10¹² Hz. The use of the unit Watts per square meter (W/m²) is more commonly associated with power per unit area irradiated, while lumens measure the total luminous flux emitted by a light source. Therefore, the most relevant measure directly related to human visual perception of light brightness is the Candela.