A current `l` flows along the length of an infinitely long, straight, thin-walled pipe. Then,
(a) the magnetic field at all points inside the pipe is the same, but not zero
(b) the magnetic field at any point inside the pipe is zero
(c) the magnetic field is zero only on the axis of the pipe
(d) the magnetic field is different at different points inside the pipe

Explanation

To solve the problem, we need to analyze the magnetic field inside an infinitely long, straight, thin-walled pipe carrying a current \( I \).

### Step-by-Step Solution:

1. **Understanding the Setup**:
- We have a hollow cylindrical pipe with a current \( I \) flowing along its length. The pipe is infinitely long and thin-walled.

2. **Applying Ampère's Law**:
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