To determine the appropriate unit for Spectral Actinic Flux, let's first understand its meaning and the context in which it is used.

Spectral Actinic Flux measures the number of photons available in a particular spectral band for chemical reactions per unit area, per unit time, and per unit wavelength.

Given this definition, let's evaluate the options:

1. \(\text{m}^{-2} \text{s}^{-1}\): This unit represents the flux per unit area per time, but it lacks the spectral/wavelength component which is essential for denoting the spectral actinic flux.
2. \(\text{cm}^{-2} \text{s}^{-1} \text{nm}^{-1}\): This unit denotes the flux per square centimeter, per second, and per nanometer of wavelength—a direct representation of the spectral component along with the spatial and temporal measurements. This is what we are looking for when expressing spectral actinic flux.
3. \(\text{cm}^{2} \text{molecule}^{-1} \text{nm}^{-1}\): This unit is typically used in the context of absorption cross-section, which involves per molecule measurement rather than photon or energy flux.
4. \(\text{W m}^{-2} \text{nm}^{-1}\): Such a unit typically measures spectral irradiance or radiance in terms of energy per unit area per wavelength, not directly related to measuring photon flux.

After evaluating all the options, the most accurate choice that represents the unit for Spectral Actinic Flux is \(\text{cm}^{-2} \text{s}^{-1} \text{nm}^{-1}\).

Thus, the correct answer is \(\text{cm}^{-2} \text{s}^{-1} \text{nm}^{-1}\).