In this item, it is assumed that what is unknown is the part of the cell in which the process of photosynthesis takes place. The answer to this item would have to be a CHLOROPLAST. This organelle of the cell contains the colored pigments which are important in the light-dependent reactions.
In most of the plants, the photosynthesis happens with the aid of the chlorophyll. This is a pigment that absorbs the red and green light while reflecting the green one. It is to be known that different pigments will have to have different responses to the stimuli (wavelengths of light).
