The instantaneous speed of a body can be measured:-

Options

A. Graphically
B. By speedometer
C. Both of above
D. vetorially

Explanation

To determine how the instantaneous speed of a body can be measured, we can analyze the options provided in the question.

### Step-by-Step Solution:

1. **Understanding Instantaneous Speed**:
- Instantaneous speed is defined as the speed of an object at a specific moment in time. It is a scalar quantity, which means it only has magnitude and no direction.

2. **Analyzing the Options**:
- The options given are:
a) Graphically
b) By speedometer
c) Both a and b
d) Vectorically

3. **Option a: Graphically**:
- Instantaneous speed can indeed be measured graphically. For instance, if you have a graph of displacement versus time, the slope of the tangent line at any point on this graph gives the instantaneous speed at that moment. Similarly, in an acceleration versus time graph, the area under the curve can be used to find the change in velocity, which can help in determining instantaneous speed.

4. **Option b: By Speedometer**:
- A speedometer is a device commonly used in vehicles to measure the instantaneous speed of the vehicle. It provides a direct reading of speed at any given moment, making it a reliable tool for measuring instantaneous speed.

5. **Option c: Both a and b**:
- Since both graphical methods and speedometers can measure instantaneous speed, this option is also correct.

6. **Option d: Vectorically**:
- This option is incorrect because while speed is a scalar quantity, velocity (which includes direction) is a vector quantity. Thus, we do not measure instantaneous speed vectorially.

7. **Conclusion**:
- The correct answer is option c) Both a and b, as both methods can be used to measure the instantaneous speed of a body.

### Final Answer:
The instantaneous speed of a body can be measured: **Both a and b (option c)**.