The movement of which ions causes the depolarisation of nerve fibre?

Explanation

### Step-by-Step Solution:

1. **Understanding Depolarization**:
- Depolarization refers to the change in the electric charge distribution across the nerve fiber's membrane. It occurs when the inside of the cell becomes less negative (or more positive) compared to the outside.

2. **Resting Phase of Nerve Fiber**:
- In the resting phase, the nerve fiber maintains a negative charge inside compared to the outside. This is due to the distribution of ions, primarily sodium (Na⁺) and potassium (K⁺).

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