Through which of the following does electric current not flow?

Options

A. Solution of hydrochloric acid
B. Copper wire
C. Solid sodium chloride
D. Molten sodium chloride

Explanation

To solve the question "Through which of the following does electric current not flow?", we will analyze each option provided.

### Step-by-Step Solution:

1. **Understand the Concept of Electric Current:**
Electric current is the flow of electric charge. It can flow through materials that have charged particles (ions or free electrons) that can move.

2. **Evaluate the First Option: Hydraulic Acid:**
- Hydraulic Acid (HCl) is a solution that dissociates into H⁺ and Cl⁻ ions when dissolved in water.
- Since it contains ions, electric current can flow through it.

3. **Evaluate the Second Option: Copper Wire:**
- Copper is a metal that has free electrons in its structure.
- These free electrons can move and carry electric current.
- Therefore, electric current can flow through copper wire.

4. **Evaluate the Third Option: Solid NaCl:**
- Solid Sodium Chloride (NaCl) consists of a lattice structure where Na⁺ and Cl⁻ ions are fixed in place and cannot move freely.
- Since there are no free-moving charged particles, electric current cannot flow through solid NaCl.

5. **Evaluate the Fourth Option: Molten Sodium Chloride:**
- When NaCl is melted, it breaks down into Na⁺ and Cl⁻ ions.
- These ions can move freely in the molten state, allowing electric current to flow through molten NaCl.

6. **Conclusion:**
- From the analysis, the only option through which electric current does not flow is **Solid Sodium Chloride (NaCl)**.

### Final Answer:
**Solid Sodium Chloride (NaCl)**