Correct Answer - d
If the paritcle at t=0 s is at mean position the maximum displacement is given by
`x=A sin (2pit)/(T)`
if it takes time `t_(1)` to move from mean position to half the displacement then
`(A)/(2)=A "sin "(2pit)/(T)` or `1/2 =" sin "(2pit)/(T)`
or `"sin "(pi)/(6)=sin (2pit)/(T)`
or ` (pi)/(6)=(2pit)/(T)`
`rarr t=(T)/(12)s`