If `a_(r )` and `a_(t)` respresent radial and tangential acceleration, the motion of a particle will be circualr is
A. `a_(r) = 0` and `a_(t) = 0`
B. `a_(r) = 0` but `a_(t) != 0`
C. `a_(r) != 0` and `a_(t) = 0`
D. `a_(r) !=0` and `a_(t) != 0`

If `a_(r )` and `a_(t)` respresent radial and tangential acceleration, the motion of a particle will be circular is
A. (i, iii)
B. (ii, iii)
C. (iii, iv)
D. (ii, iv)