Correct Answer - B
Between `C` and `D` block will move with constant speed of `120cm//s`. Therefore, period of oscillation will be (starting from `C).T = t_(CD) +(T_(2))/(2) +t_(DC) +(T_(1))/(2)`
Here, `T_(1) =2p sqrt((m)/(k_(1)))` and `T_(2) =2p sqrt(m)/(k_(2))`and `t_(CD) =t_(DC) = (60)/(120) =0.5s`
`:. T = 0.5 +(2pi)/(2) sqrt((0.2)/(3.2)) +0.5 +(2pi)/(2) sqrt((0.2)/(1.8))`
`(m = 200g =0.2 kg)T = 2.82 s`