Study the given equation of photosynthesis. Identify X, Y and Z and select the correct statement.
X + Water 
Carbohydrates + Z
I. X is the gas which constitutes 21% of air in the atmosphere.
II. Y represents the pigment present in green leaves of the plant.
III. Z is the gas which turns lime water milky.
IV. X is the gas which extinguishes fire.
AI and II
BII and IV
CI, II and III
DI, II, III and IV