B

Step 1: To determine the direction of deflection of a positively charged particle in a magnetic field, we can use the right-hand rule.
Step 2: In the given figure, the velocity vector (v) of the positively charged particle is directed towards the right (in the +x direction).
Step 3: The magnetic field (B) is directed upwards (in the +y direction).
Step 4: According to the right-hand rule, point your thumb in the direction of the velocity (v) and your fingers in the direction of the magnetic field (B).
Step 5: Your palm will point in the direction of the force experienced by the positively charged particle. In this case, your palm will point out of the plane towards the observer, which is traditionally considered as the +z direction.
Therefore, the particle will deflect towards the +y direction.
Therefore, the correct answer is B.