Correct Answer - B
Applying the conservation of momentum to the system.
`mgh = 1/2kx^(2)`
Given, m = 0.04 kg, h=5m, k= 400Nm^(-1)`
and x = deformation (compression in the spring)`
`rArr x=(sqrt(2mgh)/k) = (sqrt(2 xx 0.04 xx 10 xx 5))/400`
`=1/10 m = 10cm ~~ 9.8 cm`