When light at a wavelength of 680 or 700nm alone are shined on a leaf a similar amount of photosynthesis occurs. However, when both wavelengths are shined at the same time more than double the amount of photosynthesis occurred. Which of the following best explains this observation

A. The amount of ATP produced will be the sum of ATP produced by exciting photosystems I and II.

B. Photosystem I cannot be activated unless photosystem II is first activate.

C. When both wavelengths are used, electrons can pass from photosystem II to photosystem I generating more ATP.

D. When both wavelengths are used twice as many photons exciting photosystem II and producing twice as much ATP