The heaviest subatomic particle is

Options

A. Neutron
B. Positron
C. Electron
D. Proton

Explanation

To determine which is the heaviest subatomic particle among the neutron, positron, electron, and proton, we can follow these steps:

### Step-by-Step Solution:

1. **List the Subatomic Particles**: Identify the subatomic particles we are comparing: neutron, positron, electron, and proton.

2. **Know the Mass of Each Particle**:
- **Neutron**: The mass of a neutron is approximately 1.008664 atomic mass units (AMU).
- **Proton**: The mass of a proton is approximately 1.007276 AMU.
- **Electron**: The mass of an electron is approximately 0.000548 AMU.
- **Positron**: The mass of a positron is the same as that of an electron, which is approximately 0.000548 AMU.

3. **Compare the Masses**: Now, we compare the masses of these particles:
- Neutron: 1.008664 AMU
- Proton: 1.007276 AMU
- Electron: 0.000548 AMU
- Positron: 0.000548 AMU

4. **Identify the Heaviest Particle**: From the comparison, we can see that the neutron has the highest mass among all the listed particles.

5. **Conclusion**: Therefore, the heaviest subatomic particle is the neutron.

### Final Answer:
The heaviest subatomic particle is the **neutron**.