Circumferential and longitudinal strains in the cylindrical boiler under internal steam pressure are $$\epsilon_1 and \epsilon_2$$ respectively. Change in the volumeof the boiler cylinder per unit volumewill be

A

$$\epsilon_1 ^2 \epsilon_2$$

B

$$\epsilon_1 \epsilon_2 ^{2}$$

C

$$2\epsilon_1 + \epsilon_2$$

D

$$\epsilon_1 + 2\epsilon_2$$