Priyanka took a destarched potted plant and set up an experiment as shown in the figure. She left the plant in sunlight for few hours and then tested the leaves X and Y for starch. Leaf X did not give starch test while leaf Y showed presence of starch.
What is proved by this experiment?
A Chlorophyll is necessary for photo-synthesis.
B Carbon dioxide is necessary for photo-synthesis.
C Light is necessary for photosynthesis.
D Oxygen is given out during photo-synthesis.