Energy is .........

Options

A. the capacity to use power.
B. capacity to produce power
C. capacity to do work
D. capacity to do work per unit time.

Explanation

To solve the question "Energy is .........", we need to analyze the provided options and determine which one accurately defines energy based on scientific principles.

### Step-by-Step Solution:

1. **Understanding the Definition of Energy**:
- Energy is fundamentally defined in physics as the ability or capacity to do work. This means that energy is what allows systems to perform tasks or exert forces.

**Hint**: Recall the basic definition of energy in physics.

2. **Analyzing the Options**:
- The options given are:
1. Capacity to use work
2. Capacity to produce power
3. Capacity to do work
4. Capacity to do work per unit time

**Hint**: Look for the option that directly relates to the definition of energy.

3. **Evaluating Each Option**:
- **Option 1**: "Capacity to use work" - This is not a standard definition of energy.
- **Option 2**: "Capacity to produce power" - This relates to power, which is the rate of doing work, not energy itself.
- **Option 3**: "Capacity to do work" - This aligns perfectly with the scientific definition of energy.
- **Option 4**: "Capacity to do work per unit time" - This describes power, not energy.

**Hint**: Identify which option directly corresponds to the definition of energy.

4. **Selecting the Correct Answer**:
- Based on the analysis, the correct answer is **Option 3: Capacity to do work**.

**Hint**: Confirm that the chosen option matches the definition you have learned.

### Final Answer:
Energy is defined as the **capacity to do work**.