Positron has nearly the same mass as that of:

Options

A. `alpha`-particle
B. Proton
C. Neutron
D. Electron

Answer

To solve the question regarding the mass of a positron, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Positron**:
- A positron is defined as the antiparticle of the electron. This means it has the same mass as an electron but carries a positive charge.

2. **Mass of the Electron**:
- The mass of an electron is approximately \(9.1 \times 10^{-31}\) kg.

3. **Comparing with Other Particles**:
- We need to compare the mass of the positron with the masses of the other particles mentioned in the options:
- **Alpha Particle**: An alpha particle consists of 2 protons and 2 neutrons, making it significantly heavier than an electron or positron.
- **Proton**: The mass of a proton is approximately \(1.67 \times 10^{-27}\) kg, which is much greater than that of an electron or positron.
- **Neutron**: The mass of a neutron is also around \(1.67 \times 10^{-27}\) kg, similar to that of a proton and much heavier than an electron or positron.

4. **Conclusion**:
- Since the positron has the same mass as the electron, we conclude that the positron has nearly the same mass as that of the electron.

5. **Final Answer**:
- Therefore, the correct option is **electron** (Option 4).