Dark reaction is dependent on the productsi.e. ATP & NADPH obtained by light reaction .So option B is correct.

The function of ATP in photosynthesis is the transfer of energy from the light reaction to the dark reaction.

Photosynthesis is the process by which plants, algae, and some bacteria convert sunlight, water, and carbon dioxide into glucose and oxygen. It occurs in the chloroplasts of plant cells and involves two main stages: the light reaction and the dark reaction (also known as the Calvin cycle).

Light Reaction:
The light reaction takes place in the thylakoid membranes of the chloroplasts. It is the initial step in photosynthesis and involves the absorption of light energy by pigments such as chlorophyll. The light energy is then converted into chemical energy in the form of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate).

Dark Reaction:
The dark reaction occurs in the stroma of the chloroplasts and does not require direct sunlight. It uses the ATP and NADPH produced in the light reaction to convert carbon dioxide into glucose through a series of enzymatic reactions. This process is also known as the Calvin cycle.

Role of ATP:
ATP is an energy currency molecule that is used to transfer energy within cells. In photosynthesis, ATP plays a crucial role in transferring energy from the light reaction to the dark reaction. Here's how ATP functions in this process:

1. Light energy is absorbed by chlorophyll in the thylakoid membranes during the light reaction.
2. This energy is used to split water molecules into oxygen, hydrogen ions (H+), and electrons.
3. The electrons are passed along a series of electron carriers, generating ATP through a process called photophosphorylation.
4. The ATP molecules produced during the light reaction are then used in the dark reaction to provide energy for the synthesis of glucose.
5. In the dark reaction, ATP is hydrolyzed to ADP (adenosine diphosphate) and inorganic phosphate (Pi), releasing energy that is utilized to convert carbon dioxide into glucose.

In summary, ATP functions as an intermediate energy carrier between the light reaction and the dark reaction in photosynthesis. It captures and transfers the energy derived from sunlight to fuel the synthesis of glucose, which is essential for the growth and development of plants.