In the following arrangement the pulley is assumed to be light and the strings inextensible. The acceleration of the system can be determined by considering conservation of a certain physical quantity. The physical quantity conserved and the acceleration respectively, are

A

energy and $$\frac{g}{3}$$

B

linear momentum and $$\frac{g}{2}$$

C

angular momentum and $$\frac{g}{3}$$

D

mass and $$\frac{g}{2}$$