Which of the following items can not be used in an electric circuit so that the current can pass through them?

Options

A. Iron key
B. Copper wire
C. Matchstick
D. Silver wire

Explanation

To solve the question of which item cannot be used in an electric circuit so that the current can pass through them, we will analyze each option provided:

1. **Iron Key**:
- Iron is a metal and a good conductor of electricity. Therefore, an iron key can be used in an electric circuit to allow current to pass through it.

2. **Copper Wire**:
- Copper is also a metal and is widely known for its excellent conductivity. A copper wire can easily be used in an electric circuit for current to flow.

3. **Silver Wire**:
- Silver is the best conductor of electricity among all metals. Thus, a silver wire can be used in an electric circuit to allow current to pass through it.

4. **Matchstick**:
- A matchstick is made of wood, which is a poor conductor of electricity and acts as an insulator. Therefore, a matchstick cannot be used in an electric circuit for current to pass through.

Based on the analysis above, the item that cannot be used in an electric circuit so that the current can pass through it is the **matchstick**.

### Summary of the Solution:
- Iron Key: Conductor (can be used)
- Copper Wire: Conductor (can be used)
- Silver Wire: Conductor (can be used)
- Matchstick: Insulator (cannot be used)

### Final Answer:
**Matchstick** cannot be used in an electric circuit so that the current can pass through it.

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