Swimming is possible on account of

Options

A. Newton's laws of gravitation
B. Newton's first law of motion
C. Newton's second law of motion
D. Newton's third law of motion

Answer

To solve the question "Swimming is possible on account of," we need to analyze the options provided and apply the relevant laws of motion.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the reason why swimming is possible. We need to relate this to the laws of motion.

2. **Reviewing the Options**:
- **Option A**: Newton's law of motion (general term, not specific).
- **Option B**: Newton's first law of motion (law of inertia).
- **Option C**: Newton's second law of motion (F=ma).
- **Option D**: Newton's third law of motion (action-reaction principle).

3. **Analyzing Newton's Laws**:
- **Newton's First Law**: States that an object at rest stays at rest and an object in motion stays in motion unless acted upon by a net external force. This does not directly explain swimming.
- **Newton's Second Law**: Relates to the acceleration of an object when a force is applied. While relevant to motion, it does not specifically explain the mechanics of swimming.
- **Newton's Third Law**: States that for every action, there is an equal and opposite reaction. This is crucial for understanding swimming.

4. **Applying Newton's Third Law to Swimming**:
- When a swimmer pushes water backwards with their hands and feet, they exert a downward force on the water.
- According to Newton's third law, the water exerts an equal and opposite force on the swimmer, propelling them forward.
- This action-reaction pair is what allows the swimmer to move through the water.

5. **Conclusion**: Based on the analysis, the correct answer is **Option D: Newton's third law of motion**.

### Final Answer:
Swimming is possible on account of **Newton's third law of motion**.