The motion of a particle along a straight line is described by equation $x = 8 + 12t –t^3$ where x is in metre and t in second. The retardation of the particle when its velocity becomes zero is

Question

( A ) zero
( B ) $12 ms^{–2}$
( C ) $6 ms^{–2}$
( D ) $24ms^{–2}$