Four circles each of radius a cm are touching each other in pairs as shown in the figure. The area of the shaded region (in sq.cm) between the circular, as shown in this figure is

A

$$\frac{2a^{2}}{7}$$

B

$$\frac{4a^{2}}{7}$$

C

$$\frac{3a^{2}}{7}$$

D

$$\frac{6a^{2}}{7}$$