Which photoreceptor cells respond to the longest wavelengths of light, ranging from approximately 500-700 nm?

The rods are photoreceptor cells that respond to the longest wavelengths of light, ranging from approximately 500-700 nm. Rods are responsible for vision at low light levels (scotopic vision). 
The cones, on the otehr hand are the other photoreceptors in the human retina that are active at higher light levels (photopic vision).

The answer is c) tons