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

The light-dependent phase involves the two photosystems which get excited at a different wavelength. The PSII gets excited at 680 nm wavelength whereas the PSI gets excited at 700 nm wavelength.

When both the wavelengths of light are provided to the photosystem then the number of ATP increases as both the photosystem is activated at a different wavelength and the combined effect of the wavelength will, therefore, increase the efficiency of the photosynthesis as compared to when one type of wavelength is provided.

Thus, Option-C is the correct answer.