Head and work are equivalent.This means

Options

A. when we supply heat to a body we do work on it
B. when we do work on a body we supply heat to it
C. the temperature of a body can be increased by doing work on it
D. a body at rest may be can be set into motion along a line by suppliying heat to it

Explanation

To solve the question, we need to analyze the statement "Heat and work are equivalent" and evaluate the given options based on this concept.

### Step-by-Step Solution:

1. **Understanding the Concept**:
- Heat and work are forms of energy transfer. When heat is supplied to a system, it can increase the internal energy of the system, which may result in a temperature increase. Similarly, when work is done on a system, it can also increase the internal energy, leading to a temperature increase.

2. **Evaluating the Options**:
- **Option 1**: "When we supply heat to a body, we do work on it."
- This statement is not necessarily true. Supplying heat to a body does not mean that work is being done on it. Heat transfer can occur without any mechanical work.

- **Option 2**: "When we do work on a body, we supply heat to it."
- This statement is also not true. Doing work on a body does not automatically mean that heat is being supplied. Work can be done without heat transfer.

- **Option 3**: "The temperature of the body can be increased by doing work on it."
- This statement is true. When work is done on a body, it can lead to an increase in its internal energy, which can increase its temperature.

- **Option 4**: "A body at rest may be set into motion along a line by supplying heat to it."
- This statement is incorrect. A body can only be set into motion by applying a force (doing work), not merely by supplying heat.

3. **Conclusion**:
- Based on the analysis, the only correct option is **Option 3**: "The temperature of the body can be increased by doing work on it."

### Final Answer:
The correct option is **Option 3**.

---