The metallic cap projecting out from the top of a cell is

Options

A. switch
B. positive terminal
C. negative teminal
D. spring

Explanation

To solve the question regarding the metallic cap projecting out from the top of a cell, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of a Cell**:
- An electric cell consists of two terminals: a positive terminal and a negative terminal.

2. **Identify the Components**:
- The positive terminal is usually represented by a metallic cap that protrudes from the top of the cell.
- The negative terminal is typically a metal disk located at the bottom of the cell.

3. **Determine the Function of the Terminals**:
- The positive terminal is where the electric current flows out of the cell, while the negative terminal is where the current flows into the cell.

4. **Conclusion**:
- Since the question asks about the metallic cap projecting out from the top of a cell, we can conclude that this cap represents the positive terminal of the cell.

5. **Final Answer**:
- Therefore, the metallic cap projecting out from the top of a cell is the **positive terminal**.