Cyclic photophosphorylation occurs when only light of wavelengths _______ are available.
(i) Below 680 nm (ii) Beyond 680 nm
(iii) 400 nm and below (iv) Beyond 400 nm

Explanation

To answer the question regarding the wavelengths at which cyclic photophosphorylation occurs, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Cyclic Photophosphorylation**:
- Cyclic photophosphorylation is a process that occurs in photosynthesis where electrons are excited by light and then return to their original position after passing through an electron transport chain. This process primarily involves Photosystem I (PSI).

2. **Identifying the Key Wavelength**:
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