Question

Assertion (A): Splitting of water is associated with PS II. water splits into protons, O2 and electron.
Reason (R): The electrons needed to replace those removed from photosystem I are provided by PS II.

• A. Both (A) and (R) are correct and (R) is the correct explanation to (A)
• B. Both (A) and (R) are correct but (R) is not correct explanation for (A)
• C. (A) is correct (R) is wrong
• D. (A) is wrong (R) is correct

Hint:

Water splitting physically occurs on the inner side of the thylakoid membrane.
The protons generated accumulate in the thylakoid lumen, creating the proton gradient needed for ATP synthesis.

Answer 1

The Correct Option is B

Step 1: Check the Assertion on its own.
Water splitting happens at Photosystem II, releasing protons, oxygen and electrons. This is a settled fact of the Z-scheme, so A is true.
Step 2: Check the Reason on its own.
Photosystem I does lose electrons when it gets excited, and those electrons are indeed replaced through the electron transport chain that starts at PS II. So R is also a true statement.
Step 3: Ask whether R explains A.
A is about where water splits and what it produces. R is about how PS I gets its lost electrons back. These are two separate facts about the light reaction, and R does not actually justify why water splitting happens at PS II.
Final answer: Option 2, Both A and R are correct, but R is not the correct explanation of A.