PS I have a chlorophyll a molecule that absorbs maximum light of _ nm.

Explanation

Photosystem I (PS I) is one of the two photosystems involved in the light-dependent reactions of photosynthesis. The reaction center of PS I contains a chlorophyll-a molecule that absorbs light most efficiently at a wavelength of 700 nm, hence it is often referred to as P700. This absorption peak distinguishes it from Photosystem II, which absorbs light best at 680 nm, known as P680.Options A (600 nm) and B (650 nm) do not match the peak absorption characteristics of PS I. Option C (680 nm) is specifically characteristic of Photosystem II, not Photosystem I. Therefore, the correct answer is Option D (700 nm).