When a particle moves in a vertical circle:

Explanation

In a vertical circular motion, such as a particle on a string or a roller coaster loop, both radial and tangential accelerations vary. The gravitational force acting on the particle changes direction relative to the motion, affecting both accelerations. At the top of the circle, gravity causes the tangential component to point downward, while at the bottom, it points upward. Similarly, the radial acceleration is affected by the changing speed due to gravitational influence. This makes Option B correct as it accurately describes the nature of the motion. Options A, C, and D are incorrect because they incorrectly assume that one or both accelerations remain constant.