The correct option is B CO2 is essential for photosynthesis
Mohl’s half leaf experiment was conducted to demonstrate the importance of CO2 in photosynthesis. The part of the leaf exposed to KOH did not synthesise food through photosynthesis since KOH absorbed all the CO2 from the immediate surroundings of the leaf.
Jan Ingenhousz’s aquatic plant experiment proved that sunlight is essential for photosynthesis.
Jan Bapista van Helmont’s willow tree experiment was used to prove that water is essential for photosynthesis.
Variegated leaf experiment was used to prove that chlorophyll is essential for photosynthesis.