Task: Class Definition Understanding (ontology: Earth_Environment/OBOE)

Which of the following definitions best describes 'PhotonFluxDensity'?

A. The number of photons striking an area per unit time. This could be probably also be called a PhotonArealDensityRate.
B. is a measure of a material's ability to conduct an electric current. Units are siemens per meter
C. the concept is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. The SI unit for the concept is candela per square metre (cd/m2).
D. The developmental stage of life of a given organism.

Answer: The number of photons striking an area per unit time. This could be probably also be called a PhotonArealDensityRate.