The question pertains to the pattern of magnetic field lines around an infinitely long straight current-carrying wire. According to Ampère's Law, an infinite straight wire carrying a steady current produces a magnetic field whose lines form concentric circles around the wire.

Let's delve into the reasoning for the correct answer:

1. According to the Biot-Savart Law and Ampère's Circuital Law, the magnetic field \((\mathbf{B})\) around a straight, infinitely long current-carrying wire is given by:

\(B = \frac{\mu_0 I}{2\pi r}\)

• Where \(\mu_0\) is the permeability of free space, \(I\) is the current, and \(r\) is the radial distance from the wire.

2. The formula shows that the magnetic field strength decreases with distance from the wire, and it is directed along circular paths around the wire.

3. The right-hand rule helps visualize this: if the thumb points in the direction of the current, the fingers curl in the direction of the magnetic field lines, forming concentric circles around the wire.

Based on this analysis:

• The option "Concentric circular paths" correctly describes the pattern of magnetic field lines around an infinitely long straight current-carrying wire.

Therefore, the correct answer is Concentric circular paths.

Let's rule out other options:

• Radially outward directed lines: This would imply the field lines start at the wire and move outward, which does not align with the circular nature of magnetic fields around a straight wire.
• Straight parallel lines only: This configuration is typical of a uniform magnetic field, such as that between parallel plates, not around a wire.
• Elliptical closed trajectories: This is not applicable as magnetic field lines around a straight wire form perfect circles, not ellipses.

In conclusion, the magnetic field around an infinitely long straight current-carrying wire is characterized by concentric circular paths of magnetic field lines.