Homework Help: Zero Magnetic Force

1. The problem statement, all variables and given/known data
A proton with an initial velocity of magnitude v in the +x direction enters a uniform magnetic field. For which direction or directions of the magnetic field, if any, will there be zero magnetic force on the proton?
+ x
- x
+ y
- y
+ z
- z

2. Relevant equations
There were no equations i could think of that will help we with this problem, other than the open palm thing that my professor talked about in class today.

3. The attempt at a solution
I dont really understand the question. on the graph (+) x is in the third quadrant and thats the velocity. I tried -x by itself, i tried -x, +y, and +z. And +y, +z. All three were incorrect. I dont think i understand what it means to have zero magnetic force on a proton.