The molecules known as the energy currency of the cell are :

Options

A. NAD
B. NADP
C. ATP
D. ADP

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the molecule that is referred to as the energy currency of the cell.

2. **Analyzing the Options**:
- **Option 1: NAD (Nicotinamide Adenine Dinucleotide)**: This molecule plays a role in redox reactions but is not primarily known as the energy currency of the cell. Therefore, this option is incorrect.
- **Option 2: NADP (Nicotinamide Adenine Dinucleotide Phosphate)**: Similar to NAD, NADP is involved in anabolic reactions and is not the energy currency. Thus, this option is also incorrect.
- **Option 3: ATP (Adenosine Triphosphate)**: ATP is widely recognized as the energy currency of the cell because it stores and provides energy for various cellular processes. This option is correct.
- **Option 4: ADP (Adenosine Diphosphate)**: While ADP is related to ATP, it is not the primary energy currency. Instead, it is a product of ATP when energy is released. Therefore, this option is incorrect.

3. **Conclusion**: After analyzing all the options, we conclude that the correct answer is ATP, as it is the molecule known as the energy currency of the cell.

**Final Answer**: ATP (Adenosine Triphosphate) is the energy currency of the cell.

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