The equation
`4H^(+) rarr _(2)^(4) He^(2+) + 2e bar + 26 MeV represents`

Options

A. (a) `beta`-decay
B. (b) `gamma`-decay
C. (c) fusion
D. (d) fission

Explanation

To analyze the equation \( 4H^{+} \rightarrow (2)^{4}He^{2+} + 2\bar{e} + 26 \text{ MeV} \), we need to identify what type of nuclear reaction this represents. Let's break down the components of the equation step by step.

### Step 1: Identify the Reactants and Products
The left side of the equation shows \( 4H^{+} \), which represents four protons (hydrogen nuclei). The right side shows \( (2)^{4}He^{2+} \), which indicates the formation of a helium nucleus with a charge of +2, along with the emission of two positrons (denoted by \( 2\bar{e} \)) and a release of energy (26 MeV).

### Step 2: Determine the Type of Reaction
The reaction involves the fusion of hydrogen nuclei to form helium. In nuclear fusion, lighter nuclei combine to form a heavier nucleus, releasing energy in the process. Here, four protons combine to form one helium nucleus and two positrons.

### Step 3: Analyze the Energy Release
The equation states that 26 MeV of energy is released. This is characteristic of fusion reactions, where energy is released due to the mass defect (the difference in mass between the reactants and the products) being converted into energy according to Einstein's equation \( E=mc^2 \).

### Step 4: Conclusion
Given that the reaction involves the fusion of hydrogen nuclei to form helium and releases energy, we conclude that the equation represents a **nuclear fusion reaction**.

### Final Answer
The equation \( 4H^{+} \rightarrow (2)^{4}He^{2+} + 2\bar{e} + 26 \text{ MeV} \) represents a **nuclear fusion reaction**.

---