A helium cylinder in which the volume of gas is 2.24 L at STP (1 atm, 273 K) developed a leak and when the leak was plugged the pressure in the cylinder was seen to have dropped to 550 mm of Hg. The number of moles of He gas that had escaped due to this leak is

A

0.028

B

0.072

C

0.972

D

0.099