Read the following statements and find out the incorrect statement.

Plants in which the first product of CO₂ fixation is a C₃ acid (PGA), i.e., the C₄ pathway. 

The correct answer is Option (3)- Plants in which the first product of CO₂ fixation is a C₃ acid (PGA), i.e., the C₄ pathway.
The products of light reaction are ATP, NADPH and O₂ . Of these O₂ diffuses out of the chloroplast while ATP and NADPH are used to drive the processes leading to the synthesis of food, more accurately, sugars. This is the biosynthetic phase of photosynthesis. This process does not directly depend on the presence of light but is dependent on the products of the light reaction, i.e., ATP and NADPH, besides CO₂ and H₂O. Immediately after light becomes unavailable, the biosynthetic process continues for some time, and then stops. If then, light is made available, the synthesis starts again .

The use of radioactive ¹⁴C by him in algal photosynthesis studies led to the discovery that the first CO₂ fixation product was a 3-carbon organic acid. He also contributed to working out the complete biosynthetic pathway; hence it was called Calvin cycle after him. The first product identified was 3-phosphoglyceric acid or in short PGA.

Scientists also tried to know whether all plants have PGA as the first product of CO₂ fixation, or whether any other product was formed in other plants. Experiments conducted over a wide range of plants led to the discovery of another group of plants, where the first stable product of CO₂ fixation was again an organic acid, but one which had 4 carbon atoms in it. This acid was identified to be oxaloacetic acid or OAA.

Since then CO₂ assimilation during photosynthesis was said to be of two main types: those plants in which the first product of CO₂ fixation is a C₃ acid (PGA), i.e., the C₃ pathway, and those in which the first product was a C₄ acid (OAA), i.e., the C₄ pathway.