Two blocks of masses m and 2m are placed on a smooth horizontal surface as shown. In the first case only a force $$f_1$$ is applied from left. Later on only a force $$f_2$$ is applied from right. If the force acting at the interface of the two blocks in the two cases is the same, then $$f_1 \colon f_2$$ is

A

$$1 \colon 1$$

B

$$1 \colon 2$$

C

$$2 \colon 1$$

D

$$1 \colon 3$$