Which of the following processes represents a gamma- decay only ?

Options

A. `zX^(A) + Yto"_(z-1)X^(0) + a + b`
B. `zX^(A)+_(0)n^(0)to"_(z-1)X^(A-3) + c`
C. `zX^(A)to"_(z)X^(A) + f`
D. `zX^(A)+_(-1)l"to_(z-1)X^(A) + g`

Answer

To determine which process represents gamma decay only, we need to understand the characteristics of gamma decay.

### Step-by-Step Solution:

1. **Understanding Gamma Decay**:
- Gamma decay occurs when a nucleus is in an excited state and transitions to a lower energy state by emitting gamma radiation.
- This process does not change the atomic number (Z) or the mass number (A) of the nucleus.

2. **Identifying the Characteristics of Gamma Decay**:
- In gamma decay, the parent nucleus and the daughter nucleus have the same atomic number and mass number.
- The only product of gamma decay is gamma rays, which are high-energy photons.

3. **Analyzing the Options**:
- We need to look at the given options and identify which one shows a process where the atomic mass and atomic number remain unchanged, with gamma rays as the only byproduct.

4. **Selecting the Correct Option**:
- After reviewing the options, we find that only option C maintains the same atomic mass and atomic number for both the parent and daughter nuclei, while emitting gamma rays.

5. **Conclusion**:
- Therefore, the process that represents gamma decay only is option C.

### Final Answer:
The process that represents gamma decay only is **option C**.

---