Atomic weight of carbon = 12

Atomic weight of oxygen = 16     

12  32  44

12 kg of carbon will burn completely with 32 kg of oxygen

1 kg of carbon requires  of oxygen

Air contains 21% of oxygen by volume and 23% by weight. So, mass of air required

..Method 2..

For 12 g of carbon we need, 2x 16= 32  g of oxygen

So, for 1 kg (1000 g) we need 2666 g of oxygen, and in moles  moles of air. 

In volume it would require about 9340 L of air.

m = 9.340 m3 1.2 kg/m3 = 11.208 kg 11.6 kg

Hence, the correct option is (C).