D

Step 1: Understand that a charged particle moving in a magnetic field experiences a force given by the Lorentz force law, which is defined as F = q( extbf{v} imes extbf{B}), where q is the charge, extbf{v} is the velocity vector, and extbf{B} is the magnetic field vector. This force is always perpendicular to both the velocity of the particle and the magnetic field, causing the particle to undergo circular motion in the plane perpendicular to the magnetic field.

Step 2: If the velocity of the particle has a component along the direction of the magnetic field, then this component of velocity does not experience a magnetic force and continues in its original direction, while the perpendicular component undergoes circular motion.

Step 3: The result of this combination of motion—circular motion in the plane perpendicular to the magnetic field and linear motion along the direction of the magnetic field—results in a helical pathway.

Conclusion: Therefore, when the initial velocity is neither along nor perpendicular to the magnetic field, the charged particle traces out a helical path.
Therefore, the correct answer is D.