Two blocks of masses m1 and m2 are attached to the lower end of a light vertical spring of force constant k. The upper end of the spring is fixed. When the system is in equilibrium, the lower block (m2) drops off. The other block (m1) will
(a) remain undisturbed
(b) move up through a distance m2g/ k and come to rest
(c) undergo vertical SHM with a time period of 2π√(m1/k)
(d) undergo vertical SHM with a time period of 2π√(m1 + m2) / k