When a heavy particle collides with a light particle at rest, then after collision the target particle moves with:

Explanation

In collisions where a heavy particle (m1) collides with a much lighter particle (m2) that is initially at rest, the conservation of momentum and kinetic energy in an elastic collision dictates that the lighter particle will move with a velocity that is double the velocity of the incident heavy particle. This occurs because the heavy particle's mass is much greater than that of the lighter particle, allowing the lighter particle to gain significant speed. Option B is correct because it accurately represents this outcome in an elastic collision scenario. The other options are incorrect because they do not account for the principles of momentum and energy conservation.