Answer
Perpendicular. Parallel.
Work Step by Step
The magnetic force is maximum when the charged particle moves perpendicular to the field. It is minimum when the charged particle moves parallel to the magnetic field.
In a later physics course, you will learn that the magnetic force is proportional to the sine of the angle between the charge's velocity and the magnetic field.
The sine of $90^{\circ}$ is 1, which gives the strongest force. The sine of $0^{\circ}$ is 0, which gives no force.
This is discussed on page 460.
