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 andreleased, it oscillates with a time period of 3s. When the mass m is increased by 1kg, the time period of oscillations becomes 5s. The value of m in kg is

A

$$\frac{4}{3}$$

B

$$\frac{16}{9}$$

C

$$\frac{9}{16}$$

D

$$\frac{3}{4}$$