An equation for the incomplete combustion of butane in oxygen is

1 mole of butane uses 4.5 moles of oxygen
0.1 mole of butane will use = 0.1 * 4.5 = 0.45 moles
 
P = 100 kPa = 100,000Pa
n = 0.45
T = 295 K
V = ?

Using PV = nRT
⇒ 100,000 * V = 0.45 * 8.314 * 295
⇒100,000 V = 1103.68
⇒ V = 1103.68/100,000 m³
⇒ V = 1103.68/100,000 * 1000 dm³
⇒ V = 11.036 dm³

You need 11.036 dm³ oxygen.

The answer should be c.