Correct Answer - `(4)`
For circular platform,
`R = 0.5 m , M = 0.45 kg`
For toy : `m = 0.05 kg, r = 0.25 m , v = 9 ms^(-1)`
According to law of consevation of angular momentum
`2 xx mvr = I omega = (MR^(2))/(2) omega`
or `omega = (4mvr)/(MR^(2)) = (4 xx 0.05 xx 9 xx 0.25)/(0.45 xx (0.5)^(2)) = 4 rad//s`