A particle moves in a circle describing equal angle in equal times, its velocity vector

The correct option is C change in direction
Let the particle describes an angle $\theta$ radian in time $t$ second.

$\therefore$ Angular velocity $w=\frac{\theta }{t}$ rad/s

Thus its linear velocity $v=rw=\frac{r\theta }{t}=constant$

Hence the magnitude of velocity is constant.

But the velocity vector is tangential to the circular motion, thus it changes its direction at every instant.