If a plant lacks chlorophyll, which process will be affected first?

Correct answer: Photosynthesis

Chlorophyll is the green pigment that absorbs light energy needed to drive photosynthesis. In its absence or severe deficiency, the leaf cannot efficiently convert carbon dioxide and water into glucose, so food formation is affected directly and first. Transpiration, water transport and mineral absorption may continue through other structures, although plant growth can later suffer. Therefore option A is correct.