A body of mass m is attached to the lower end of a spring whose upper end is fixed. The spring has negligible mass. When the mass m is slightly pulled down and released, it oscillates with a time period of 3s. When the mass m is increased by `1 kg`, the time period of oscillations becomes 5s. The value of m in kg is
A. `(3)/(4)`
B. `(4)/(3)`
C. `(16)/(9)`
D. `(9)/(16)`