How are photosynthetic pigments organized?

Explanation

Photosynthetic pigments are organized into clusters called 'photosystems' in the thylakoid membranes. These clusters are crucial for capturing light energy during the lightdependent reactions of photosynthesis. Option D is correct because it acknowledges both the clustering of pigments and their designation as photosystems. Option A is partially correct but does not specify the term 'photosystems'. Option B correctly identifies the term 'photosystems' but does not highlight the clustering aspect. Option C is incorrect because 'stacks' refer to the thylakoid membrane arrangement, not the organization of pigments.