In the process of photosynthesis,the plants take (CO2) &(H2O).....
plants breaks (H2O) to form O2. Hence, O2 comes from (H2O)

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**Explanation:**

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. During this process, oxygen is released as a byproduct. The oxygen liberated during photosynthesis comes specifically from water (H2O).

**Photosynthesis:**

Photosynthesis occurs in the chloroplasts of plant cells, specifically in the chlorophyll-containing organelles called chloroplasts. The process can be divided into two main stages:

1. **Light-dependent reactions:** These reactions occur in the thylakoid membranes of the chloroplasts and require light energy. During this stage, light energy is absorbed by chlorophyll pigments, and water molecules are split into oxygen, protons (H+), and electrons. The oxygen molecules are released as a byproduct, while the protons and electrons are used in the next stage.

2. **Light-independent reactions (Calvin cycle):** These reactions occur in the stroma of the chloroplasts and do not directly require light. In this stage, the protons and electrons produced in the light-dependent reactions are used to convert carbon dioxide (CO2) into glucose. This process is known as carbon fixation.

**Oxygen Liberation:**

The oxygen liberated during photosynthesis comes from the splitting of water molecules in the light-dependent reactions. The reaction can be summarized as follows:

2H2O + 2NADP+ + 3ADP + 3Pi + light energy → O2 + 2NADPH + 3ATP

In this reaction, two water molecules are split, resulting in the release of one molecule of oxygen (O2) and the production of two molecules of reduced nicotinamide adenine dinucleotide phosphate (NADPH) and three molecules of adenosine triphosphate (ATP). The oxygen is released into the atmosphere as a byproduct.

Therefore, the correct answer is option A) H2O, as the oxygen liberated during photosynthesis comes from the splitting of water molecules.