Which of the following speed - time `(upsilon-t)` graph is physically not possible ?

Options

A.
B.
C.
D. All of these

Explanation

To determine which of the given speed-time graphs is physically not possible, we will analyze each option based on the properties of speed and the characteristics of speed-time graphs.

### Step-by-Step Solution:

1. **Understanding Speed-Time Graphs**:
- A speed-time graph represents the relationship between speed (the magnitude of velocity) and time.
- Speed is always a non-negative quantity; it cannot be negative.

2. **Analyzing Option A**:
- In the graph for Option A, if we draw a vertical line at a specific time, we observe that there are two different speeds corresponding to the same time.
- This implies that the speed is not uniquely defined for that instant, which is not physically possible.
- **Conclusion**: Option A is not possible.

3. **Analyzing Option B**:
- Similar to Option A, in the graph for Option B, drawing a vertical line at a specific time also shows two different speeds for that same time.
- Again, this means the speed is not uniquely defined, which is also not physically possible.
- **Conclusion**: Option B is not possible.

4. **Analyzing Option C**:
- In the graph for Option C, we notice that the speed is represented as a negative value.
- Since speed cannot be negative, this representation is not physically possible.
- **Conclusion**: Option C is not possible.

5. **Final Conclusion**:
- Since all three options (A, B, and C) are not possible based on the analysis, the answer is that all of them are physically not possible.
- Therefore, the correct answer is Option D: All of the above are not possible.