Answer:
Letter A
Explanation:
From the description you make, it's likely that the structure with letter A is the chloroplast. It is round and small and it's free because of the pigment needed for photosynthesis (chlorophyll). It is located inside the cell, suspended in the cytoplasm.
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<span> In the process of photosynthesis, chlorophyll goes into a peculiar excited state which can survive for an unusually long time. Furthermore, the excitation energy can hope from chlorophyll molecule to chlorophyll molecule. In this way a large collection of chlorphyll molecules function as an "antenna" that collects many photons and funnels their energy down to a reaction center, where one particular chlorophyll will lose an electron.</span>
It's called the Promoter Region.
