Assertion: The proton gradient is broken down due to the movement of protons across the membrane to stroma through the transmembrane channerl of the `F_(0)` of the ATPase.
Reason: The breakdonw of proton gradient leads to release of energy.

Answer

B

Explanation

Electron transport in photosynthesis produces a proton gradient. The gradient develops inside the thylakoid lumen in chloroplasts. Proton gradient or high concentration of `H^(+)` in the lumen. The protom gradient is broken down due to movement of protons through tramembrane channes, `F_(0)` of ATPase. The break donw of the gradient provides enough energy to cause a confomational change in the `F_(1)` particle of the ATPase, which makes the enzyme synthesise several molecules of energy-packed ATP.